High statistics analysis using anisotropic clover lattices: (III) Baryon-baryon interactions
Beane, S; Detmold, W; Lin, H; Luu, T; Orginos, K; Savage, M; Torok, A; Walker-Loud, A
2010-01-19
Low-energy baryon-baryon interactions are calculated in a high-statistics lattice QCD study on a single ensemble of anisotropic clover gauge-field configurations at a pion mass of m{sub {pi}} {approx} 390 MeV, a spatial volume of L{sup 3} {approx} (2.5 fm){sup 3}, and a spatial lattice spacing of b {approx} 0.123 fm. Luescher's method is used to extract nucleon-nucleon, hyperon-nucleon and hyperon-hyperon scattering phase shifts at one momentum from the one- and two-baryon ground-state energies in the lattice volume. The isospin-3/2 N{Sigma} interactions are found to be highly spin-dependent, and the interaction in the {sup 3}S{sub 1} channel is found to be strong. In contrast, the N{Lambda} interactions are found to be spin-independent, within the uncertainties of the calculation, consistent with the absence of one-pion-exchange. The only channel for which a negative energy-shift is found is {Lambda}{Lambda}, indicating that the {Lambda}{Lambda} interaction is attractive, as anticipated from model-dependent discussions regarding the H-dibaryon. The NN scattering lengths are found to be small, clearly indicating the absence of any fine-tuning in the NN-sector at this pion mass. This is consistent with our previous Lattice QCD calculation of NN interactions. The behavior of the signal-to-noise ratio in the baryon-baryon correlation functions, and in the ratio of correlation functions that yields the ground-state energy splitting is explored. In particular, focus is placed on the window of time slices for which the signal-to-noise ratio does not degrade exponentially, as this provides the opportunity to extract quantitative information about multi-baryon systems.
High Statistics Analysis using Anisotropic Clover Lattices: (III) Baryon-Baryon Interactions
Silas Beane; Detmold, William; Lin, Huey-Wen; Luu, Thomas C.; Orginos, Kostas; Savage, Martin; Torok, Aaron M.; Walker-Loud, Andre
2010-03-01
Low-energy baryon-baryon interactions are calculated in a high-statistics lattice QCD study on a single ensemble of anisotropic clover gauge-field configurations at a pion mass of m_pi ~ 390 MeV, a spatial volume of L^3 ~ (2.5 fm)^3, and a spatial lattice spacing of b ~ 0.123 fm. Luscher’s method is used to extract nucleon-nucleon, hyperon-nucleon and hyperon-hyperon scattering phase shifts at one momentum from the one- and two-baryon ground-state energies in the lattice volume. The N-Sigma interactions are found to be highly spin-dependent, and the interaction in the ^3 S _1 channel is found to be strong. In contrast, the N-Lambda interactions are found to be spin-independent, within the uncertainties of the calculation, consistent with the absence of one-pion-exchange. The only channel for which a negative energy-shift is found is Lambda-Lambda, indicating that the Lambda-Lambda interaction is attractive, as anticipated from model-dependent discussions regarding the H-dibaryon. The NN scattering lengths are found to be small, clearly indicating the absence of any fine-tuning in the NN-sector at this pion mass. This is consistent with our previous Lattice QCD calculation of the NN interactions. The behavior of the signal-to-noise ratio in the baryon-baryon correlation functions, and in the ratio of correlation functions that yields the ground-state energy splitting
Baryon-baryon mixing in hypernuclei
Gibson, B.F.
1998-12-31
Implications of few-body hypernuclei for the understanding of the baryon-baryon interaction are examined. Octet-octet coupling effects not present in conventional, non strange nuclei are the focus. The need to identify strangeness {minus}2 hypernuclei to test model predictions is emphasized.
Baryon-Baryon Interactions ---Nijmegen Extended-Soft-Core Models---
NASA Astrophysics Data System (ADS)
Rijken, T. A.; Nagels, M. M.; Yamamoto, Y.
We review the Nijmegen extended-soft-core (ESC) models for the baryon-baryon (BB) interactions of the SU(3) flavor-octet of baryons (N, Lambda, Sigma, and Xi). The interactions are basically studied from the meson-exchange point of view, in the spirit of the Yukawa-approach to the nuclear force problem [H. Yukawa, ``On the interaction of Elementary Particles I'', Proceedings of the Physico-Mathematical Society of Japan 17 (1935), 48], using generalized soft-core Yukawa-functions. These interactions are supplemented with (i) multiple-gluon-exchange, and (ii) structural effects due to the quark-core of the baryons. We present in some detail the most recent extended-soft-core model, henceforth referred to as ESC08, which is the most complete, sophisticated, and successful interaction-model. Furthermore, we discuss briefly its predecessor the ESC04-model [Th. A. Rijken and Y. Yamamoto, Phys. Rev. C 73 (2006), 044007; Th. A. Rijken and Y. Yamamoto, Ph ys. Rev. C 73 (2006), 044008; Th. A. Rijken and Y. Yamamoto, nucl-th/0608074]. For the soft-core one-boson-exchange (OBE) models we refer to the literature [Th. A. Rijken, in Proceedings of the International Conference on Few-Body Problems in Nuclear and Particle Physics, Quebec, 1974, ed. R. J. Slobodrian, B. Cuec and R. Ramavataram (Presses Universitè Laval, Quebec, 1975), p. 136; Th. A. Rijken, Ph. D. thesis, University of Nijmegen, 1975; M. M. Nagels, Th. A. Rijken and J. J. de Swart, Phys. Rev. D 17 (1978), 768; P. M. M. Maessen, Th. A. Rijken and J. J. de Swart, Phys. Rev. C 40 (1989), 2226; Th. A. Rijken, V. G. J. Stoks and Y. Yamamoto, Phys. Rev. C 59 (1999), 21; V. G. J. Stoks and Th. A. Rijken, Phys. Rev. C 59 (1999), 3009]. All ingredients of these latter models are also part of ESC08, and so a description of ESC08 comprises all models so far in principle. The extended-soft-core (ESC) interactions consist of local- and non-local-potentials due to (i) one-boson-exchanges (OBE), which are the members of nonets of
Extended-soft-core baryon-baryon model. II. Hyperon-nucleon interaction
NASA Astrophysics Data System (ADS)
Rijken, Th. A.; Yamamoto, Y.
2006-04-01
The YN results are presented from the extended soft-core (ESC) interactions. They consist of local and nonlocal potentials because of (i) one-boson exchanges (OBE), which are the members of nonets of pseudoscalar, vector, scalar, and axial mesons; (ii) diffractive exchanges; (iii) two-pseudoscalar exchange; and (iv) meson-pair exchange (MPE). Both the OBE and pair vertices are regulated by Gaussian form factors producing potentials with a soft behavior near the origin. The assignment of the cutoff masses for the baryon-baryon-meson (BBM) vertices is dependent on the SU(3) classification of the exchanged mesons for OBE and a similar scheme for MPE. The particular version of the ESC model, called ESC04 [T. A. Rijken, Phys. Rev. C 73, 044007 (2006)], describes nucleon-nucleon (NN) and hyperon-nucleon (YN) interactions in a unified way using broken SU(3) symmetry. Novel ingredients are the inclusion of (i) the axial-vector meson potentials and (ii) a zero in the scalar- and axial-vector meson form factors. These innovations made it possible for the first time to keep the parameters of the model close to the predictions of the 3P0 quark-antiquark creation model. This is also the case for the F/(F+D) ratios. Furthermore, the introduction of the zero helped to avoid the occurrence of unwanted bound states. Broken SU(3) symmetry serves to connect the NN and the YN channels, which leaves after fitting NN only a few free parameters for the determination of the YN interactions. In particular, the meson-baryon coupling constants are calculated via SU(3) using the coupling constants of the NN analysis as input. Here, as a novel feature, medium-strong flavor-symmetry breaking (FSB) of the coupling constants was allowed, using the 3P0 model with a Gell-Mann-Okubo hypercharge breaking for the BBM coupling. Very good fits for ESC model with and without FSB were obtained. The charge-symmetry breaking in the Λp and Λn channels, which is an SU(2) isospin breaking, is included in the
Extended-soft-core baryon-baryon model. II. Hyperon-nucleon interaction
Rijken, Th.A.; Yamamoto, Y.
2006-04-15
The YN results are presented from the extended soft-core (ESC) interactions. They consist of local and nonlocal potentials because of (i) one-boson exchanges (OBE), which are the members of nonets of pseudoscalar, vector, scalar, and axial mesons; (ii) diffractive exchanges; (iii) two-pseudoscalar exchange; and (iv) meson-pair exchange (MPE). Both the OBE and pair vertices are regulated by Gaussian form factors producing potentials with a soft behavior near the origin. The assignment of the cutoff masses for the baryon-baryon-meson (BBM) vertices is dependent on the SU(3) classification of the exchanged mesons for OBE and a similar scheme for MPE. The particular version of the ESC model, called ESC04 [T. A. Rijken, Phys. Rev. C 73, 044007 (2006)], describes nucleon-nucleon (NN) and hyperon-nucleon (YN) interactions in a unified way using broken SU(3) symmetry. Novel ingredients are the inclusion of (i) the axial-vector meson potentials and (ii) a zero in the scalar- and axial-vector meson form factors. These innovations made it possible for the first time to keep the parameters of the model close to the predictions of the {sup 3}P{sub 0} quark-antiquark creation model. This is also the case for the F/(F+D) ratios. Furthermore, the introduction of the zero helped to avoid the occurrence of unwanted bound states. Broken SU(3) symmetry serves to connect the NN and the YN channels, which leaves after fitting NN only a few free parameters for the determination of the YN interactions. In particular, the meson-baryon coupling constants are calculated via SU(3) using the coupling constants of the NN analysis as input. Here, as a novel feature, medium-strong flavor-symmetry breaking (FSB) of the coupling constants was allowed, using the {sup 3}P{sub 0} model with a Gell-Mann-Okubo hypercharge breaking for the BBM coupling. Very good fits for ESC model with and without FSB were obtained. The charge-symmetry breaking in the {lambda}p and {lambda}n channels, which is an SU(2
Lattice dynamics study of bismuth III V compounds
NASA Astrophysics Data System (ADS)
Belabbes, A.; Zaoui, A.; Ferhat, M.
2008-10-01
We present first-principles calculations of the structural and lattice-dynamical properties for cubic bismuth III-V compounds: BBi, AlBi and GaBi. The ground-state properties, i.e., the lattice constant and the bulk modulus, are calculated using a plane wave pseudopotential method within density functional theory. A linear-response approach to density functional theory is used to derive the phonon frequencies. The effect of pressure on the dynamical charges and the longitudinal optical-transverse optical splitting is also examined.
III-V/Silicon Lattice-Matched Tandem Solar Cells
Geisz, J.; Olson, J.; Friedman, D.; Kurtz, S.; McMahon, W.; Romero, M.; Reedy, R.; Jones, K.; Norman, A.; Duda, A.; Kibbler, A.; Kramer, C.; Young, M.
2005-01-01
A two-junction device consisting of a 1.7-eV GaNPAs junction on a 1.1-eV silicon junction has the theoretical potential to achieve nearly optimal efficiency for a two-junction tandem cell. We have demonstrated a monolithic III-V-on-silicon tandem solar cell in which most of the III-V layers are nearly lattice-matched to the silicon substrate. The cell includes a GaNPAs top cell, a GaP-based tunnel junction (TJ), and a diffused silicon junction formed during the epitaxial growth of GaNP on the silicon substrate. To accomplish this, we have developed techniques for the growth of high crystalline quality lattice-matched GaNPAs on silicon by metal-organic vapor-phase epitaxy.
Fujiwara, Y.; Kohno, M.; Miyagawa, K.; Suzuki, Y.
2004-10-01
The previous Faddeev calculation of the two-alpha plus {lambda} system for {sub {lambda}}{sup 9}Be is extended to incorporate the spin-orbit components of the SU{sub 6} quark-model (QM) baryon-baryon interactions. We employ the Born kernel of the QM {lambda}N LS interaction and generate the spin-orbit component of the {lambda}{alpha} potential by {alpha}-cluster folding. The Faddeev calculation in the jj-coupling scheme implies that the direct use of the QM Born kernel for the {lambda}N LS component is not good enough to reproduce the small experimental value {delta}E{sub ls}{sup expt}=43{+-}5 keV for the 5/2{sup +}-3/2{sup +} splitting. This procedure predicts 3-5 times larger values in the models FSS and fss2. The spin-orbit contribution from the effective meson-exchange potentials in fss2 is argued to be unfavorable to the small ls splitting, through the analysis of the Scheerbaum factors for the single-particle spin-orbit potentials calculated in the G-matrix formalism.
Extended-soft-core baryon-baryon model. I. Nucleon-nucleon scattering with the ESC04 interaction
Rijken, Th.A.
2006-04-15
The NN results are presented from the extended-soft-core (ESC) interactions. They consist of local and nonlocal potentials due to (i) one-boson-exchanges (OBE), which are the members of nonets of pseudoscalar, vector, scalar, and axial mesons (ii) diffractive exchanges (iii) two-pseudoscalar exchanges (PS-PS), and (iv) meson-pair exchanges (MPE). We describe a fit to the pp and np data for 0{<=}T{sub lab}{<=}350 MeV, having a typical {chi}{sup 2}/N{sub data}=1.155. Here, we used {approx}20 quasi-free physical parameters, which are coupling constants and cutoff masses. A remarkable feature of the couplings is that we were able to require them to follow rather closely the pattern predicted by the {sup 3}P{sub 0} quark-pair-creation (QPC) model. As a result the 11 OBE couplings are rather constrained, i.e., quasi free. Also, the deuteron binding energy and the several NN scattering lengths are fitted.
Lattice-Mismatched III-V Epilayers for High-Efficiency Photovoltaics
Ahrenkiel, Scott Phillip
2013-06-30
The project focused on development of new approaches and materials combinations to expand and improve the quality and versatility of lattice-mismatched (LMM) III-V semiconductor epilayers for use in high-efficiency multijunction photovoltaic (PV) devices. To address these goals, new capabilities for materials synthesis and characterization were established at SDSM&T that have applications in modern opto- and nano-electronics, including epitaxial crystal growth and transmission electron microscopy. Advances were made in analyzing and controlling the strain profiles and quality of compositional grades used for these technologies. In particular, quaternary compositional grades were demonstrated, and a quantitative method for characteristic X-ray analysis was developed. The project allowed enhanced collaboration between scientists at NREL and SDSM&T to address closely related research goals, including materials exchange and characterization.
Compositional and Structural Characterization by TEM of Lattice-Mismatched III-V Epilayers
Ahrenkiel, S. P.; Rathi, M.; Nesheim, R.; Zheng, N.; Vunnam, S.; Carapella, J. J.; Wanlass, M. W.
2011-01-01
We discuss compositional and structural transmission electron microscopy (TEM) characterization of lattice-mismatched (LMM) III-V epilayers grown on GaAs by metalorganic chemical vapor deposition (MOCVD), with possible applications in high-efficiency multijunction solar cells. In addition to the use of TEM imaging to survey layer thicknesses and defect morphology, our analysis emphasizes the particular methods of energy-dispersive X-ray spectrometry (EDX) and convergent-beam electron diffraction (CBED). Outlined here is a standards-based method for extracting compositions by EDX, which uses principal-component analysis (PCA) [1], combined with the zeta-factor approach of Watanabe and Williams [2]. A procedure is described that uses the coordinates of high-order Laue zone (HOLZ) lines, which are found in the bright-field disks of CBED patterns, to extract composition and strain parameters from embedded epilayers. The majority of the crystal growth for this work was performed at NREL, which has accommodated the development at SDSM&T of the characterization techniques described. However, epilayer deposition capability at SDSM&T has recently been achieved, using a home-built system, which is presently being used to examine new lattice-mismatched structures relevant to photovoltaic technology.
Case for exotic baryon-baryon states
Thomas, G.H.
1980-01-01
Three main points are presented. (1) Current theoretical prejudices are presented for why dibaryon states are interesting, and why they should be expected. (2) A review is given of some of the unsettled experimental issues which have emerged during this conference concerning dibaryons. (3) Phenomenological issues are raised which are critical to understanding whether dibaryon states are observable in the medium energy NN system.
2D and 3D Anilato-Based Heterometallic M(I)M(III) Lattices: The Missing Link.
Benmansour, Samia; Vallés-García, Cristina; Gómez-Claramunt, Patricia; Mínguez Espallargas, Guillermo; Gómez-García, Carlos J
2015-06-01
The similar bis-bidentate coordination mode of oxalato and anilato-based ligands is exploited here to create the first examples of 2D and 3D heterometallic lattices based on anilato ligands combining M(I) and a M(III) ions, phases already observed with oxalato but unknown with anilato-type ligands. These lattices are prepared with alkaline metal ions and magnetic chiral tris(anilato)metalate molecular building blocks: [M(III)(C6O4X2)3](3-) (M(III) = Fe and Cr; X = Cl and Br; (C6O4X2)(2-) = dianion of the 3,6-disubstituted derivatives of 2,5-dihydroxy-1,4-benzoquinone, H4C6O4). The new compounds include two very similar 2D lattices formulated as (PBu3Me)2[NaCr(C6O4Br2)3] (1) and (PPh3Et)2[KFe(C6O4Cl2)3](dmf)2 (2), both presenting hexagonal [M(I)M(III)(C6O4X2)3](2-) honeycomb layers with (PBu3Me)(+) in 1 or (PPh3Et)(+) and dmf in 2 inserted between them. Minor modifications in the synthetic conditions yield the novel 3D lattice (NEt3Me)[Na(dmf)][NaFe(C6O4Cl2)3] (3), in which hexagonal layers analogous to 1 and 2 are interconnected through Na(+) cations, and (NBu3Me)2[NaCr(C6O4Br2)3] (4), the first heterometallic 3D lattice based on anilato ligands. This compound presents two interlocked chiral 3D (10,3) lattices with opposite chiralities. Attempts to prepare 4 in larger quantities result in the 2D polymorph of compound 4 (4'). Magnetic properties of compounds 1, 3, and 4' are reported, and in all cases we observe, as expected, paramagnetic behaviors that can be satisfactorily reproduced with simple monomer models including a zero field splitting (ZFS) of the corresponding S = 3/2 for Cr(III) in 1 and 4' or S = 5/2 for Fe(III) in 3. PMID:25965415
NASA Astrophysics Data System (ADS)
Frentrup, Martin; Hatui, Nirupam; Wernicke, Tim; Stellmach, Joachim; Bhattacharya, Arnab; Kneissl, Michael
2013-12-01
In group-III-nitride heterostructures with semipolar or nonpolar crystal orientation, anisotropic lattice and thermal mismatch with the buffer or substrate lead to a complex distortion of the unit cells, e.g., by shearing of the lattice. This makes an accurate determination of lattice parameters, composition, and strain state under assumption of the hexagonal symmetry impossible. In this work, we present a procedure to accurately determine the lattice constants, strain state, and composition of semipolar heterostructures using high resolution X-ray diffraction. An analysis of the unit cell distortion shows that four independent lattice parameters are sufficient to describe this distortion. Assuming only small deviations from an ideal hexagonal structure, a linear expression for the interplanar distances dhkl is derived. It is used to determine the lattice parameters from high resolution X-ray diffraction 2ϑ-ω-scans of multiple on- and off-axis reflections via a weighted least-square fit. The strain and composition of ternary alloys are then evaluated by transforming the elastic parameters (using Hooke's law) from the natural crystal-fixed coordinate system to a layer-based system, given by the in-plane directions and the growth direction. We illustrate our procedure taking an example of (112¯2) AlκGa1-κN epilayers with Al-contents over the entire composition range. We separately identify the in-plane and out-of-plane strains and discuss origins for the observed anisotropy.
Chu Wenjuan; He Yong; Zhao Qinghuan; Fan Yaoting; Hou Hongwei
2010-10-15
Two novel inorganic-organic 3D network, namely{l_brace}[Ln(L){sub 1.5}(H{sub 2}O){sub 2}].5H{sub 2}O{r_brace}n [Ln=Y (1), Ce (2); Ln(L){sub 1.5}(H{sub 2}O){sub 2}].5H{sub 2}O [Ln=Y (1), Ce (2)], have been prepared through the assembly of the ligand 1,2-bis[3-(1,2,4-triazolyl)-4-amino-5-carboxylmethylthio]ethane (H{sub 2}L) and lanthanide (III) salts under hydrothermal condition and structurally characterized by single-crystal X-ray diffractions. In complexes 1 and 2, the L{sup 2-} anions adopt three different coordination fashions (bidentate chelate, bidentate bridging and bidentate chelate bridging) connecting Ln(III) ions via the oxygen atoms from carboxylate moieties. Both 1 and 2 exhibit 3D network structures with 2-fold interpenetration. Interestingly, the reversible desorption-adsorption behavior of lattice water is significantly observed in the two compounds. The result shows their potential application as late-model water absorbent in the field of adsorption material. - Graphical abstract: Two inorganic-organic 3D network, namely {l_brace}[Ln(L){sub 1.5}(H{sub 2}O){sub 2}].5H{sub 2}O{r_brace}n [Ln=Y (1), Ce (2)], have been prepared under hydrothermal condition and structurally characterized by single-crystal X-ray diffractions. Both 1 and 2 exhibit 3D network structures with 2-fold interpenetration. Interestingly, the reversible desorption-adsorption behavior of lattice water is significantly observed in the two compounds. The result shows their potential application as late-model water absorbent in the field of adsorption material.
NASA Astrophysics Data System (ADS)
Morelli, D. T.; Heremans, J. P.; Slack, G. A.
2002-11-01
The isotope effect on the lattice thermal conductivity for group IV and group III-V semiconductors is calculated using the Debye-Callaway model modified to include both transverse and longitudinal phonon modes explicitly. The frequency and temperature dependences of the normal and umklapp phonon-scattering rates are kept the same for all compounds. The model requires as adjustable parameters only the longitudinal and transverse phonon Grüneisen constants and the effective sample diameter. The model can quantitatively account for the observed isotope effect in diamond and germanium but not in silicon. The magnitude of the isotope effect is predicted for silicon carbide, boron nitride, and gallium nitride. In the case of boron nitride the predicted increase in the room-temperature thermal conductivity with isotopic enrichment is in excess of 100%. Finally, a more general method of estimating normal phonon-scattering rate coefficients for other types of solids is presented.
Nucleation, Growth, and Strain Relaxation of Lattice-Mismatched III-V Semiconductor Epitaxial Layers
NASA Technical Reports Server (NTRS)
Welser, R. E.; Guido, L. J.
1994-01-01
We have investigated the early stages of evolution of highly strained 2-D InAs layers and 3-D InAs islands grown by metal-organic chemical vapor deposition (MOCVD) on (100) and (111) B GaAs substrates. The InAs epilayer / GaAs substrate combination has been chosen because the lattice-mismatch is severe (approx. 7.20%), yet these materials are otherwise very similar. By examining InAs-on-GaAs composites Instead of the more common In(x)Ga(1-x)As alloy, we remove an additional degree of freedom (x) and thereby simplify data interpretation. A matrix of experiments is described in which the MOCVD growth parameters -- susceptor temperature, TMIn flux, and AsH3 flux -- have been varied over a wide range. Scanning electron microscopy, atomic force microscopy, transmission electron microscopy, and electron microprobe analysis have been employed to observe the thin film surface morphology. In the case of 3-D growth, we have extracted activation energies and power-dependent exponents that characterize the nucleation process. As a consequence, optimized growth conditions have been identified for depositing approx. 250 A thick (100) and (111)B oriented InAs layers with relatively smooth surfaces. Together with preliminary data on the strain relaxation of these layers, the above results on the evolution of thin InAs films indicate that the (111)B orientation is particularly promising for yielding lattice-mismatched films that are fully relaxed with only misfit dislocations at the epilayer / substrate interface.
Achirality in the low temperature structure and lattice modes of tris(acetylacetonate)iron(iii).
Ellis, Thomas K; Kearley, Gordon J; Piltz, Ross O; Jayasooriya, Upali A; Stride, John A
2016-05-10
Tris(acetylacteonate) iron(iii) is a relatively ubiquitous mononuclear inorganic coordination complex. The bidentate nature of the three acetylacteonate ligands coordinating around a single centre inevitably leads to structural isomeric forms, however whether or not this relates to chirality in the solid state has been questioned in the literature. Variable temperature neutron diffraction data down to T = 3 K, highlights the dynamic nature of the ligand environment, including the motions of the hydrogen atoms. The Fourier transform of the molecular dynamics simulation based on the experimentally determined structure was shown to closely reproduce the low temperature vibrational density of states obtained using inelastic neutron scattering. PMID:27109447
Zadrozny, Joseph M; Graham, Michael J; Krzyaniak, Matthew D; Wasielewski, Michael R; Freedman, Danna E
2016-08-01
A counterintuitive three-order of magnitude slowing of the spin-lattice relaxation rate is observed in a high spin qubit at high magnetic field via multifrequency pulsed electron paramagnetic resonance measurements. PMID:27463410
Baryon-Baryon-Meson Coupling Constants in QCD
Aliev, T. M.; Ozpineci, A.; Savci, M.; Azizi, K.; Zamiralov, V.
2010-12-22
The strong coupling constant of decuplet and octet baryons to vector and pseudoscalar mesons are calculated in light cone QCD sum rules in general case and when the SU(3){sub f} symmetry is taken into account. A comparison of the obtained results with the existing experimental data and predictions of the other nonperturbative approaches is also made.
2015-01-01
The study of inorganic crystalline materials by solid-state NMR spectroscopy is often complicated by the low sensitivity of heavy nuclei. However, these materials often contain or can be prepared with paramagnetic dopants without significantly affecting the structure of the crystalline host. Dynamic nuclear polarization (DNP) is generally capable of enhancing NMR signals by transferring the magnetization of unpaired electrons to the nuclei. Therefore, the NMR sensitivity in these paramagnetically doped crystals might be increased by DNP. In this paper we demonstrate the possibility of efficient DNP transfer in polycrystalline samples of [Co(en)3Cl3]2·NaCl·6H2O (en = ethylenediamine, C2H8N2) doped with Cr(III) in varying concentrations between 0.1 and 3 mol %. We demonstrate that 1H, 13C, and 59Co can be polarized by irradiation of Cr(III) with 140 GHz microwaves at a magnetic field of 5 T. We further explain our findings on the basis of electron paramagnetic resonance spectroscopy of the Cr(III) site and analysis of its temperature-dependent zero-field splitting, as well as the dependence of the DNP enhancement factor on the external magnetic field and microwave power. This first demonstration of DNP transfer from one paramagnetic metal ion to its diamagnetic host metal ion will pave the way for future applications of DNP in paramagnetically doped materials or metalloproteins. PMID:25069794
The Flavor Structure of the Excited Baryon Spectra from Lattice QCD
Edwards, Robert G.; Mathur, Nilmani; Richards, David G.; Wallace, Stephen J
2013-03-01
Excited state spectra are calculated using lattice QCD for baryons that can be formed from $u$, $d$ and $s$ quarks, namely the $N$, $\\Delta$, $\\Lambda$, $\\Sigma$, $\\Xi$ and $\\Omega$ families of baryons. Baryonic operators are constructed from continuum operators that transform as irreducible representations of SU(3)$_F$ symmetry for flavor, SU(4) symmetry for Dirac spins of quarks and O(3) symmetry for orbital angular momenta. Covariant derivatives are used to realize orbital angular momenta. Using the operators, we calculate matrices of correlation functions in order to extract excited states. The resulting lattice spectra have bands of baryonic states with well-defined total spins up to $J=7/2$. Each state can be assigned a dominant flavor symmetry and the counting of states of each flavor and spin reflects $SU(6) \\times O(3)$ symmetry for the lowest negative-parity and positive-parity bands. States with strong hybrid content are identified through the dominance of chromo-magnetic operators.
Lattice Dynamical Properties of Group-III Nitrides AN (A = B, Al, Ga and In) in Zinc-Blende Phase
NASA Astrophysics Data System (ADS)
Kushwaha, A. K.
2016-03-01
In the present paper, we have calculated the phonon dispersion relations, phonon density of states, Debye characteristic temperature and the zone boundary phonons for group-III nitrides AN (A = B, Al, Ga and In) using eleven-parameter three-body shell model with both the ions being polarizable. Our calculated results are in good agreement with experimental results available in the literature.
NASA Astrophysics Data System (ADS)
Jacobsen, Jesper Lykke; Salas, Jesús; Sokal, Alan D.
2003-09-01
We study the chromatic polynomial P G ( q) for m× n triangular-lattice strips of widths m≤12P,9F (with periodic or free transverse boundary conditions, respectively) and arbitrary lengths n (with free longitudinal boundary conditions). The chromatic polynomial gives the zero-temperature limit of the partition function for the q-state Potts antiferromagnet. We compute the transfer matrix for such strips in the Fortuin-Kasteleyn representation and obtain the corresponding accumulation sets of chromatic zeros in the complex q-plane in the limit n→∞. We recompute the limiting curve obtained by Baxter in the thermodynamic limit m, n→∞ and find new interesting features with possible physical consequences. Finally, we analyze the isolated limiting points and their relation with the Beraha numbers.
Qubit Control Limited by Spin-Lattice Relaxation in a Nuclear Spin-Free Iron(III) Complex.
Zadrozny, Joseph M; Freedman, Danna E
2015-12-21
High-spin transition metal complexes are of interest as candidates for quantum information processing owing to the tunability of the pairs of MS levels for use as quantum bits (qubits). Thus, the design of high-spin systems that afford qubits with stable superposition states is of primary importance. Nuclear spins are a potent instigator of superposition instability; thus, we probed the Ph4P(+) salt of the nuclear spin-free complex [Fe(C5O5)3](3-) (1) to see if long-lived superpositions were possible in such a system. Continuous-wave and pulsed electron paramagnetic resonance (EPR) spectroscopic measurements reveal a strong EPR transition at X-band that can be utilized as a qubit. However, at 5 K the coherent lifetime, T2, for this resonance is 721(3) ns and decreases rapidly with increasing temperature. Simultaneously, the spin-lattice relaxation time is extremely short, 11.33(1) μs, at 5 K, and also rapidly decreases with increasing temperature. The coincidence of these two temperature-dependent data sets suggests that T2 in 1 is strongly limited by the short T1. Importantly, these results highlight the need for new design parameters in pursuit of high-spin species with appreciable coherence times. PMID:26650962
NASA Astrophysics Data System (ADS)
Guter, W.; Kern, R.; Köstler, W.; Kubera, T.; Löckenhoff, R.; Meusel, M.; Shirnow, M.; Strobl, G.
2011-12-01
AZUR SPACE's current CPV product 3C40C is an advanced lattice-matched In0.50Ga0.50P/In0.01Ga0.99As/Ge triple junction (3J) solar cell. Recently, efficiencies up to 41.2% (450-600×AM1.5d) have been confirmed for this 40%-class product. This kind of solar cell structure has now reached its practical efficiency limit and went into production in 2010. AZUR offers customized cell structures, regarding size and grid design, as well as anti-reflection coatings adapted to the individual CPV system. Integration grades from diced wafers up to assemblies, such as dense arrays, are available. Special features and production results for the 3C40C structure are presented in this work. In order to further push efficiencies beyond 42% AZUR has successfully transferred the upright metamorphic cell from Fraunhofer ISE and advances this concept now for production. First results on metamorphic 3J solar cells at AZUR SPACE and the actual potential of this concept will be discussed. A target efficiency of 42% seems to be realistic.
NASA Astrophysics Data System (ADS)
Brambilla, M.; Di Renzo, F.; Hasegawa, M.
2014-07-01
This is the third of a series of papers on three-loop computation of renormalization constants for Lattice QCD. Our main points of interest are results for the regularization defined by the Iwasaki gauge action and Wilson fermions. Our results for quark bilinears renormalized according to the RI'-MOM scheme can be compared to non-perturbative results. The latter are available for twisted mass QCD: being defined in the chiral limit, the renormalization constants must be the same. We also address more general problems. In particular, we discuss a few methodological issues connected to summing the perturbative series such as the effectiveness of boosted perturbation theory and the disentanglement of irrelevant and finite-volume contributions. Discussing these issues we consider not only the new results of this paper, but also those for the regularization defined by the tree-level Symanzik improved gauge action and Wilson fermions, which we presented in a recent paper of ours. We finally comment on the extent to which the techniques we put at work in the NSPT context can provide a fresher look into the lattice version of the RI'-MOM scheme.
EXAMINATION OF DISLOCATIONS IN LATTICE-MISMATCHED GaInAs/BUFFER LAYER/GaAs FOR III-V PHOTOVOLTAICS
Levander, A.; Geisz, J.
2007-01-01
Dislocations act as sites for nonradiative electron/hole pair recombination, which reduces the effi ciency of photovoltaics. Lattice-matched materials can be grown on top of one another without forming a high density of dislocations. However, when the growth of lattice-mismatched (LMM) materials is attempted, many dislocations result from the relaxation of strain in the crystal structure. In an attempt to reduce the number of dislocations that propagate into a solar device when using LMM materials, a compositionally step-graded buffer is placed between the two LMM materials. In order to confi ne the dislocations to the buffer layer and therefore increase material quality and device effi ciency, the growth temperature and thickness of the buffer layer were varied. A GaInP compositionally graded buffer and GaInAs p-n junction were grown on a GaAs substrate in a metal-organic chemical vapor deposition (MOCVD) system. A multibeam optical stress sensor (MOSS) and X-ray diffraction (XRD) were used to characterize the strain in the epilayers. Electrical and optoelectronic properties were measured using a probe station and multimeter setup, solar simulator, and a quantum effi ciency instrument. It was determined that device functionality was highly dependent on the growth temperature of the graded buffer. As growth temperature increased, so did the dislocation density in the device despite an increase in the dislocation velocity, which should have increased the dislocation annihilation rate and the diffusion of dislocations to the edge of the crystal. The thickness of the graded buffer also affected device effi ciency with thinner samples performing poorly. The thinner graded buffer layers had high internal resistances from reduced carrier concentrations. In terms of effi ciency, the empirically derived recipe developed by the scientists at the National Renewable Energy Laboratory (NREL) produced the highest quality cells.
Bornyakov, V.G.
2005-06-01
Possibilities that are provided by a lattice regularization of QCD for studying nonperturbative properties of QCD are discussed. A review of some recent results obtained from computer calculations in lattice QCD is given. In particular, the results for the QCD vacuum structure, the hadron mass spectrum, and the strong coupling constant are considered.
NASA Astrophysics Data System (ADS)
Webster, P. T.; Shalindar, A. J.; Riordan, N. A.; Gogineni, C.; Liang, H.; Sharma, A. R.; Johnson, S. R.
2016-06-01
The optical properties of bulk InAs0.936Bi0.064 grown by molecular beam epitaxy on a (100)-oriented GaSb substrate are measured using spectroscopic ellipsometry. The index of refraction and absorption coefficient are measured over photon energies ranging from 44 meV to 4.4 eV and are used to identify the room temperature bandgap energy of bulk InAs0.936Bi0.064 as 60.6 meV. The bandgap of InAsBi is expressed as a function of Bi mole fraction using the band anticrossing model and a characteristic coupling strength of 1.529 eV between the Bi impurity state and the InAs valence band. These results are programmed into a software tool that calculates the miniband structure of semiconductor superlattices and identifies optimal designs in terms of maximizing the electron-hole wavefunction overlap as a function of transition energy. These functionalities are demonstrated by mapping the design spaces of lattice-matched GaSb/InAs0.911Sb0.089 and GaSb/InAs0.932Bi0.068 and strain-balanced InAs/InAsSb, InAs/GaInSb, and InAs/InAsBi superlattices on GaSb. The absorption properties of each of these material systems are directly compared by relating the wavefunction overlap square to the absorption coefficient of each optimized design. Optimal design criteria are provided for key detector wavelengths for each superlattice system. The optimal design mid-wave infrared InAs/InAsSb superlattice is grown using molecular beam epitaxy, and its optical properties are evaluated using spectroscopic ellipsometry and photoluminescence spectroscopy.
K{sup +} production in baryon-baryon and heavy-ion collisions
Li, G.Q.; Ko, C.M.; Chung, W.S.
1998-01-01
Kaon production cross sections in nucleon-nucleon, nucleon-{Delta}, and {Delta}-{Delta} interactions are studied in a boson exchange model. For the latter two interactions, the exchanged pion can be on-mass shell; only contributions due to a virtual pion are included via the Peierls method by taking into account the finite {Delta} width. With these cross sections and also those for pion-baryon interactions, subthreshold kaon production from heavy-ion collisions is studied in the relativistic transport model. {copyright} {ital 1998} {ital The American Physical Society}
ERIC Educational Resources Information Center
Parris, Richard
2011-01-01
Given a segment that joins two lattice points in R[superscript 3], when is it possible to form a lattice cube that uses this segment as one of its twelve edges? A necessary and sufficient condition is that the length of the segment be an integer. This paper presents an algorithm for finding such a cube when the prime factors of the length are…
Lattice gas and lattice Boltzmann computational physics
Chen, S.
1993-05-01
Recent developments of the lattice gas automata method and its extension to the lattice Boltzmann method have provided new computational schemes for solving a variety of partial differential equations and modeling different physics systems. The lattice gas method, regarded as the simplest microscopic and kinetic approach which generates meaningful macroscopic dynamics, is fully parallel and can be easily programmed on parallel machines. In this talk, the author will review basic principles of the lattice gas and lattice Boltzmann method, its mathematical foundation and its numerical implementation. A detailed comparison of the lattice Boltzmann method with the lattice gas technique and other traditional numerical schemes, including the finite-difference scheme and the pseudo-spectral method, for solving the Navier-Stokes hydrodynamic fluid flows, will be discussed. Recent achievements of the lattice gas and the the lattice Boltzmann method and their applications in surface phenomena, spinodal decomposition and pattern formation in chemical reaction-diffusion systems will be presented.
ERIC Educational Resources Information Center
Scott, Paul
2006-01-01
A lattice is a (rectangular) grid of points, usually pictured as occurring at the intersections of two orthogonal sets of parallel, equally spaced lines. Polygons that have lattice points as vertices are called lattice polygons. It is clear that lattice polygons come in various shapes and sizes. A very small lattice triangle may cover just 3…
Heat conduction of symmetric lattices
NASA Astrophysics Data System (ADS)
Nie, Linru; Yu, Lilong; Zheng, Zhigang; Shu, Changzheng
2013-06-01
Heat conduction of symmetric Frenkel-Kontorova (FK) lattices with a coupling displacement was investigated. Through simplifying the model, we derived analytical expression of thermal current of the system in the overdamped case. By means of numerical calculations, the results indicate that: (i) As the coupling displacement d equals to zero, temperature oscillations of the heat baths linked with the lattices can control magnitude and direction of the thermal current; (ii) Whether there is a temperature bias or not, the thermal current oscillates periodically with d, whose amplitudes become greater and greater; (iii) As d is not equal to zero, the thermal current monotonically both increases and decreases with temperature oscillation amplitude of the heat baths, dependent on values of d; (iv) The coupling displacement also induces nonmonotonic behaviors of the thermal current vs spring constant of the lattice and coupling strength of the lattices; (v) These dynamical behaviors come from interaction of the coupling displacement with periodic potential of the FK lattices. Our results have the implication that the coupling displacement plays a crucial role in the control of heat current.
Lattice QCD production on commodity clusters at Fermilab
D. Holmgren et al.
2003-09-30
We describe the construction and results to date of Fermilab's three Myrinet-networked lattice QCD production clusters (an 80-node dual Pentium III cluster, a 48-node dual Xeon cluster, and a 128-node dual Xeon cluster). We examine a number of aspects of performance of the MILC lattice QCD code running on these clusters.
Atmospheric Science Data Center
2015-12-30
ACRIM III Data and Information Active Cavity Radiometer Irradiance ... the ACRIMSAT spacecraft on December 20, 1999. ACRIM III data are reprocessed every 90 days to utilize instrument recalibration. ... ACRIM III Instrument Team Page ACRIM II Data Sets SCAR-B Block: SCAR-B Products ...
Palmer, R.B.
1987-05-01
This paper looks at, and compares three types of damping ring lattices: conventional, wiggler lattice with finite ..cap alpha.., wiggler lattice with ..cap alpha.. = 0, and observes the attainable equilibrium emittances for the three cases assuming a constraint on the attainable longitudinal impedance of 0.2 ohms. The emittance obtained are roughly in the ratio 4:2:1 for these cases.
Triton and hypertriton binding energies with SU{sub 6} quark-model baryon-baryon interactions
Fujiwara, Y.; Suzuki, Y.; Kohno, M.; Miyagawa, K.
2008-04-29
Previously we calculated the binding energies of the triton and hypertriton, using an SU{sub 6} quark-model interaction which is obtained by a resonating-group method for two baryon clusters. In contrast to the previous calculations employing the energy-dependent interaction kernel, we present new results using a renormalized interaction which is energy-independent and still preserves all the two-baryon data. The new binding energies are slightly smaller than the previous values. In particular the triton binding energy turns out to be 8.14 MeV with a charge-dependence correction of the two-nucleon force, 190 keV, being included. This indicates that the energy to be accounted for by three-body forces is about 350 keV.
Fujiwara, Y.; Suzuki, Y.; Kohno, M.; Miyagawa, K.
2008-02-15
Previously we calculated the binding energies of the triton and hypertriton, using an SU{sub 6} quark-model interaction obtained by a resonating-group method of two baryon clusters. In contrast to the previous calculations employing the energy-dependent interaction kernel, we present new results using a renormalized interaction that is energy-independent and still preserves all the two-baryon data. The new binding energies are slightly smaller than the previous values. In particular the triton binding energy turns out to be 8.14 MeV with a charge-dependence correction of the two-nucleon force, 190 keV, being included. This indicates that the energy to be accounted for by three-body forces is about 350 keV.
Baryon-baryon interactions in the SU6 quark model and their applications to light nuclear systems
NASA Astrophysics Data System (ADS)
Fujiwara, Y.; Suzuki, Y.; Nakamoto, C.
2007-04-01
Interactions between the octet-baryons ( B8) in the spin-flavor SU6 quark model are investigated in a unified coupled-channels framework of the resonating-group method (RGM). The interaction Hamiltonian for quarks consists of the phenomenological confinement potential, the color Fermi-Breit interaction with explicit flavor-symmetry breaking (FSB), and effective-meson exchange potentials of scalar-, pseudoscalar- and vector-meson types. The model parameters are determined to reproduce the properties of the nucleon-nucleon ( NN) system and the low-energy cross section data for the hyperon-nucleon interactions. Mainly due to the introduction of the vector mesons, the NN phase shifts at non-relativistic energies up to T=350 MeV are greatly improved in comparison with the previous quark-model NN interactions. The deuteron properties and the low-energy observables of the B8B8 interactions, including the inelastic capture ratio at rest for the Σ-p scattering, are examined in the particle basis with the pion-Coulomb correction. The nuclear saturation properties and the single-particle (s.p.) potentials of B8 in nuclear medium are examined through the G-matrix calculations, using the quark-exchange kernel. The Σ s.p. potential is weakly repulsive in symmetric nuclear matter. The s.p. spin-orbit strength for Λ is very small, due to the strong antisymmetric spin-orbit force generated from the Fermi-Breit interaction. The qualitative behavior of the B8B8 interactions is systematically understood by (1) the spin-flavor SU6 symmetry of B8, (2) the special role of the pion exchange, and (3) the FSB of the underlying quark Hamiltonian. In particular, the B8B8 interaction becomes less attractive according to the increase of strangeness, implying that there exists no B8B8 di-baryon bound state except for the deuteron. The strong ΛN-ΣN coupling results from the important tensor component of the one-pion exchange. The ΛΛ-ΞN-ΣΣ coupling in the strangeness S=-2 and isospin I=0 channel is relatively weak, since this coupling is caused by the strangeness exchange. The B8B8 interactions are then applied to some of the few-baryon systems and light Λ-hypernuclei in a three-cluster Faddeev formalism using two-cluster RGM kernels. An application to the three-nucleon system shows that the quark-model NN interaction can give a sufficient triton binding energy with little room for the three-nucleon force. The hypertriton Faddeev calculation indicates that the attraction of the ΛN interaction in the S01 state is only slightly more attractive than that in the S13 state. In the application to the ααΛ system, the energy spectrum of BeΛ9 is well reproduced using the αα RGM kernel. The very small spin-orbit splitting of the BeΛ9 excited states is also discussed. In the ΛΛα Faddeev calculation, the NAGARA event for HeΛΛ6 is found to be consistent with the quark-model ΛΛ interaction.
III-V arsenide-nitride semiconductor
NASA Technical Reports Server (NTRS)
Major, Jo S. (Inventor); Welch, David F. (Inventor); Scifres, Donald R. (Inventor)
2000-01-01
III-V arsenide-nitride semiconductor are disclosed. Group III elements are combined with group V elements, including at least nitrogen and arsenic, in concentrations chosen to lattice match commercially available crystalline substrates. Epitaxial growth of these III-V crystals results in direct bandgap materials, which can be used in applications such as light emitting diodes and lasers. Varying the concentrations of the elements in the III-V materials varies the bandgaps, such that materials emitting light spanning the visible spectra, as well as mid-IR and near-UV emitters, can be created. Conversely, such material can be used to create devices that acquire light and convert the light to electricity, for applications such as full color photodetectors and solar energy collectors. The growth of the III-V material can be accomplished by growing thin layers of elements or compounds in sequences that result in the overall lattice match and bandgap desired.
Lattice matched crystalline substrates for cubic nitride semiconductor growth
Norman, Andrew G; Ptak, Aaron J; McMahon, William E
2015-02-24
Disclosed embodiments include methods of fabricating a semiconductor layer or device and devices fabricated thereby. The methods include, but are not limited to, providing a substrate having a cubic crystalline surface with a known lattice parameter and growing a cubic crystalline group III-nitride alloy layer on the cubic crystalline substrate by coincident site lattice matched epitaxy. The cubic crystalline group III-nitride alloy may be prepared to have a lattice parameter (a') that is related to the lattice parameter of the substrate (a). The group III-nitride alloy may be a cubic crystalline In.sub.xGa.sub.yAl.sub.1-x-yN alloy. The lattice parameter of the In.sub.xGa.sub.yAl.sub.1-x-yN or other group III-nitride alloy may be related to the substrate lattice parameter by (a')= 2(a) or (a')=(a)/ 2. The semiconductor alloy may be prepared to have a selected band gap.
NASA Astrophysics Data System (ADS)
Sjöström, M.; Wallén, E.; Eriksson, M.; Lindgren, L.-J.
2009-04-01
One of the primary goals of the 700 MeV MAX III synchrotron radiation source is to test and gain experience with new magnet and accelerator technology. Each magnet cell is machined out of two solid iron blocks that are then sandwiched together after coil and quadrupole installation. The MAX III ring makes extensive use of combined function magnets to obtain a compact lattice. In order to obtain flexibility in machine tuning pole face current strips are used in the main dipoles, which also contain the horizontally defocusing gradients. Commissioning finished in 2007 and MAX III is now going into user operation. Over the last year, MAX III has been characterized in order to both obtain calibrated models for operation purposes as well as evaluating the magnet technology. The characterization results will be described in this paper.
Janse Van Rensburg, E.J.
1996-12-31
The geometry of polygonal knots in the cubic lattice may be used to define some knot invariants. One such invariant is the minimal edge number, which is the minimum number of edges necessary (and sufficient) to construct a lattice knot of given type. In addition, one may also define the minimal (unfolded) surface number, and the minimal (unfolded) boundary number; these are the minimum number of 2-cells necessary to construct an unfolded lattice Seifert surface of a given knot type in the lattice, and the minimum number of edges necessary in a lattice knot to guarantee the existence of an unfolded lattice Seifert surface. In addition, I derive some relations amongst these invariants. 8 refs., 5 figs., 2 tabs.
Atmospheric Science Data Center
2016-06-15
SAGE III Data and Information The Stratospheric Aerosol and Gas ... on the spacecraft. SAGE III produced L1 and L2 scientific data from 5/07/2002 until 12/31/2005. The flight of the second instrument is as ... Guide Documents: Project Guide Data Products User's Guide (PDF) Relevant Documents: ...
NASA Astrophysics Data System (ADS)
Bergner, Georg; Catterall, Simon
2016-08-01
We discuss the motivations, difficulties and progress in the study of supersymmetric lattice gauge theories focusing in particular on 𝒩 = 1 and 𝒩 = 4 super-Yang-Mills in four dimensions. Brief reviews of the corresponding lattice formalisms are given and current results are presented and discussed. We conclude with a summary of the main aspects of current work and prospects for the future.
Flat Band Quastiperiodic Lattices
NASA Astrophysics Data System (ADS)
Bodyfelt, Joshua; Flach, Sergej; Danieli, Carlo
2014-03-01
Translationally invariant lattices with flat bands (FB) in their band structure possess irreducible compact localized flat band states, which can be understood through local rotation to a Fano structure. We present extension of these quasi-1D FB structures under incommensurate lattices, reporting on the FB effects to the Metal-Insulator Transition.
Laterally closed lattice homomorphisms
NASA Astrophysics Data System (ADS)
Toumi, Mohamed Ali; Toumi, Nedra
2006-12-01
Let A and B be two Archimedean vector lattices and let be a lattice homomorphism. We call that T is laterally closed if T(D) is a maximal orthogonal system in the band generated by T(A) in B, for each maximal orthogonal system D of A. In this paper we prove that any laterally closed lattice homomorphism T of an Archimedean vector lattice A with universal completion Au into a universally complete vector lattice B can be extended to a lattice homomorphism of Au into B, which is an improvement of a result of M. Duhoux and M. Meyer [M. Duhoux and M. Meyer, Extended orthomorphisms and lateral completion of Archimedean Riesz spaces, Ann. Soc. Sci. Bruxelles 98 (1984) 3-18], who established it for the order continuous lattice homomorphism case. Moreover, if in addition Au and B are with point separating order duals (Au)' and B' respectively, then the laterally closedness property becomes a necessary and sufficient condition for any lattice homomorphism to have a similar extension to the whole Au. As an application, we give a new representation theorem for laterally closed d-algebras from which we infer the existence of d-algebra multiplications on the universal completions of d-algebras.
Björner, Anders
1987-01-01
A continuous analogue to the partition lattices is presented. This is the metric completion of the direct limit of a system of embeddings of the finite partition lattices. The construction is analogous to von Neumann's construction of a continuous geometry over a field F from the finite-dimensional projective geometries over F. PMID:16593874
Honeycomb lattices with defects
NASA Astrophysics Data System (ADS)
Spencer, Meryl A.; Ziff, Robert M.
2016-04-01
In this paper, we introduce a variant of the honeycomb lattice in which we create defects by randomly exchanging adjacent bonds, producing a random tiling with a distribution of polygon edges. We study the percolation properties on these lattices as a function of the number of exchanged bonds using an alternative computational method. We find the site and bond percolation thresholds are consistent with other three-coordinated lattices with the same standard deviation in the degree distribution of the dual; here we can produce a continuum of lattices with a range of standard deviations in the distribution. These lattices should be useful for modeling other properties of random systems as well as percolation.
Courant, E.D.; Garren, A.A.
1985-10-01
A realistic, distributed interaction region (IR) lattice has been designed that includes new components discussed in the June 1985 lattice workshop. Unlike the test lattices, the lattice presented here includes utility straights and the mechanism for crossing the beams in the experimental straights. Moreover, both the phase trombones and the dispersion suppressors contain the same bending as the normal cells. Vertically separated beams and 6 Tesla, 1-in-1 magnets are assumed. Since the cells are 200 meters long, and have 60 degree phase advance, this lattice has been named RLD1, in analogy with the corresponding test lattice, TLD1. The quadrupole gradient is 136 tesla/meter in the cells, and has similar values in other quadrupoles except in those in the IR`s, where the maximum gradient is 245 tesla/meter. RLD1 has distributed IR`s; however, clustered realistic lattices can easily be assembled from the same components, as was recently done in a version that utilizes the same type of experimental and utility straights as those of RLD1.
NASA Astrophysics Data System (ADS)
Weidner, Carrie; Yu, Hoon; Anderson, Dana
2016-05-01
In this work, we report on progress towards performing interferometry using atoms trapped in an optical lattice. That is, we start with atoms in the ground state of an optical lattice potential V(x) =V0cos [ 2 kx + ϕ(t) ] , and by a prescribed phase function ϕ(t) , transform from one atomic wavefunction to another. In this way, we implement the standard interferometric sequence of beam splitting, propagation, reflection, reverse propagation, and recombination. Through the use of optimal control techniques, we have computationally demonstrated a scalable accelerometer that provides information on the sign of the applied acceleration. Extension of this idea to a two-dimensional shaken-lattice-based gyroscope is discussed. In addition, we report on the experimental implementation of the shaken lattice system.
ORGINOS,K.
2003-01-07
I review the current status of hadronic structure computations on the lattice. I describe the basic lattice techniques and difficulties and present some of the latest lattice results; in particular recent results of the RBC group using domain wall fermions are also discussed. In conclusion, lattice computations can play an important role in understanding the hadronic structure and the fundamental properties of Quantum Chromodynamics (QCD). Although some difficulties still exist, several significant steps have been made. Advances in computer technology are expected to play a significant role in pushing these computations closer to the chiral limit and in including dynamical fermions. RBC has already begun preliminary dynamical domain wall fermion computations [49] which we expect to be pushed forward with the arrival of QCD0C. In the near future, we also expect to complete the non-perturbative renormalization of the relevant derivative operators in quenched QCD.
Superalloy Lattice Block Structures
NASA Technical Reports Server (NTRS)
Nathal, M. V.; Whittenberger, J. D.; Hebsur, M. G.; Kantzos, P. T.; Krause, D. L.
2004-01-01
Initial investigations of investment cast superalloy lattice block suggest that this technology will yield a low cost approach to utilize the high temperature strength and environmental resistance of superalloys in lightweight, damage tolerant structural configurations. Work to date has demonstrated that relatively large superalloy lattice block panels can be successfully investment cast from both IN-718 and Mar-M247. These castings exhibited mechanical properties consistent with the strength of the same superalloys measured from more conventional castings. The lattice block structure also accommodates significant deformation without failure, and is defect tolerant in fatigue. The potential of lattice block structures opens new opportunities for the use of superalloys in future generations of aircraft applications that demand strength and environmental resistance at elevated temperatures along with low weight.
Automated Lattice Perturbation Theory
Monahan, Christopher
2014-11-01
I review recent developments in automated lattice perturbation theory. Starting with an overview of lattice perturbation theory, I focus on the three automation packages currently "on the market": HiPPy/HPsrc, Pastor and PhySyCAl. I highlight some recent applications of these methods, particularly in B physics. In the final section I briefly discuss the related, but distinct, approach of numerical stochastic perturbation theory.
Legless locomotion in lattices
NASA Astrophysics Data System (ADS)
Schiebel, Perrin; Dai, Jin; Gong, Chaohui; Serrano, Miguel M.; Mendelson, Joseph R., III; Choset, Howie; Goldman, Daniel I.
2015-03-01
By propagating waves from head to tail, limbless organisms like snakes can traverse terrain composed of rocks, foliage, soil and sand. Previous research elucidated how rigid obstacles influence snake locomotion by studying a model terrain-symmetric lattices of pegs placed in hard ground. We want to understand how different substrate-body interaction modes affect performance in desert-adapted snakes during transit of substrates composed of both rigid obstacles and granular media (GM). We tested Chionactis occipitalis, the Mojave shovel-nosed snake, in two laboratory treatments: lattices of 0 . 64 cm diameter obstacles arrayed on both a hard, slick substrate and in a GM of ~ 0 . 3 mm diameter glass particles. For all lattice spacings, d, speed through the hard ground lattices was less than that in GM lattices. However, maximal undulation efficiencies ηu (number of body lengths advanced per undulation cycle) in both treatments were comparable when d was intermediate. For other d, ηu was lower than this maximum in hard ground lattices, while on GM, ηu was insensitive to d. To systematically explore such locomotion, we tested a physical robot model of the snake; performance depended sensitively on base substrate, d and body wave parameters.
ERIC Educational Resources Information Center
Allegheny County Community Coll., Pittsburgh, PA.
Instructional objectives and performance requirements are outlined in this course guide for Welding III, an advanced course in arc welding offered at the Community College of Allegheny County to provide students with the proficiency necessary for industrial certification. The course objectives, which are outlined first, specify that students will…
LandView III is a desktop mapping system that includes database extracts from the Environmental Protection Agency, the Bureau of the Census, The U.S. Geological Survey, the Nuclear Regulatory Commission, the Department of Transportation, and the Federal Emergency Management Agenc...
NASA Astrophysics Data System (ADS)
Knuth, Kevin H.
2009-12-01
Previous derivations of the sum and product rules of probability theory relied on the algebraic properties of Boolean logic. Here they are derived within a more general framework based on lattice theory. The result is a new foundation of probability theory that encompasses and generalizes both the Cox and Kolmogorov formulations. In this picture probability is a bi-valuation defined on a lattice of statements that quantifies the degree to which one statement implies another. The sum rule is a constraint equation that ensures that valuations are assigned so as to not violate associativity of the lattice join and meet. The product rule is much more interesting in that there are actually two product rules: one is a constraint equation arises from associativity of the direct products of lattices, and the other a constraint equation derived from associativity of changes of context. The generality of this formalism enables one to derive the traditionally assumed condition of additivity in measure theory, as well introduce a general notion of product. To illustrate the generic utility of this novel lattice-theoretic foundation of measure, the sum and product rules are applied to number theory. Further application of these concepts to understand the foundation of quantum mechanics is described in a joint paper in this proceedings.
III-V Growth on Silicon Toward a Multijunction Cell
Geisz, J.; Olson, J.; McMahon, W.; Friedman, D.; Kibbler, A.; Kramer, C.; Young, M.; Duda, A.; Ward, S.; Ptak, A.; Kurtz, S.; Wanlass, M.; Ahrenkiel, P.; Jiang, C. S.; Moutinho, H.; Norman, A.; Jones, K.; Romero, M.; Reedy, B.
2005-11-01
A III-V on Si multijunction solar cell promises high efficiency at relatively low cost. The challenges to epitaxial growth of high-quality III-Vs on Si, though, are extensive. Lattice-matched (LM) dilute-nitride GaNPAs solar cells have been grown on Si, but their performance is limited by defects related to the nitrogen. Advances in the growth of lattice-mismatched (LMM) materials make more traditional III-Vs, such as GaInP and GaAsP, very attractive for use in multijunction solar cells on silicon.
Lattice Boltzmann Stokesian dynamics.
Ding, E J
2015-11-01
Lattice Boltzmann Stokesian dynamics (LBSD) is presented for simulation of particle suspension in Stokes flows. This method is developed from Stokesian dynamics (SD) with resistance and mobility matrices calculated using the time-independent lattice Boltzmann algorithm (TILBA). TILBA is distinguished from the traditional lattice Boltzmann method (LBM) in that a background matrix is generated prior to the calculation. The background matrix, once generated, can be reused for calculations for different scenarios, thus the computational cost for each such subsequent calculation is significantly reduced. The LBSD inherits the merits of the SD where both near- and far-field interactions are considered. It also inherits the merits of the LBM that the computational cost is almost independent of the particle shape. PMID:26651812
Latticed pentamode acoustic cloak
Chen, Yi; Liu, Xiaoning; Hu, Gengkai
2015-01-01
We report in this work a practical design of pentamode acoustic cloak with microstructure. The proposed cloak is assembled by pentamode lattice made of a single-phase solid material. The function of rerouting acoustic wave round an obstacle has been demonstrated numerically. It is also revealed that shear related resonance due to weak shear resistance in practical pentamode lattices punctures broadband feature predicted based on ideal pentamode cloak. As a consequence, the latticed pentamode cloak can only conceal the obstacle in segmented frequency ranges. We have also shown that the shear resonance can be largely reduced by introducing material damping, and an improved broadband performance can be achieved. These works pave the way for experimental demonstration of pentamode acoustic cloak. PMID:26503821
Lattice Boltzmann Stokesian dynamics
NASA Astrophysics Data System (ADS)
Ding, E. J.
2015-11-01
Lattice Boltzmann Stokesian dynamics (LBSD) is presented for simulation of particle suspension in Stokes flows. This method is developed from Stokesian dynamics (SD) with resistance and mobility matrices calculated using the time-independent lattice Boltzmann algorithm (TILBA). TILBA is distinguished from the traditional lattice Boltzmann method (LBM) in that a background matrix is generated prior to the calculation. The background matrix, once generated, can be reused for calculations for different scenarios, thus the computational cost for each such subsequent calculation is significantly reduced. The LBSD inherits the merits of the SD where both near- and far-field interactions are considered. It also inherits the merits of the LBM that the computational cost is almost independent of the particle shape.
Catterall, Simon; Kaplan, David B.; Unsal, Mithat
2009-03-31
We provide an introduction to recent lattice formulations of supersymmetric theories which are invariant under one or more real supersymmetries at nonzero lattice spacing. These include the especially interesting case of N = 4 SYM in four dimensions. We discuss approaches based both on twisted supersymmetry and orbifold-deconstruction techniques and show their equivalence in the case of gauge theories. The presence of an exact supersymmetry reduces and in some cases eliminates the need for fine tuning to achieve a continuum limit invariant under the full supersymmetry of the target theory. We discuss open problems.
NASA Astrophysics Data System (ADS)
Singh, Kevin; Geiger, Zachary; Senaratne, Ruwan; Rajagopal, Shankari; Fujiwara, Kurt; Weld, David; Weld Group Team
2015-05-01
Quasiperiodicity is intimately involved in quantum phenomena from localization to the quantum Hall effect. Recent experimental investigation of quasiperiodic quantum effects in photonic and electronic systems have revealed intriguing connections to topological phenomena. However, such experiments have been limited by the absence of techniques for creating tunable quasiperiodic structures. We propose a new type of quasiperiodic optical lattice, constructed by intersecting a Gaussian beam with a 2D square lattice at an angle with an irrational tangent. The resulting potential, a generalization of the Fibonacci lattice, is a physical realization of the mathematical ``cut-and-project'' construction which underlies all quasiperiodic structures. Calculation of the energies and wavefunctions of atoms loaded into the proposed quasiperiodic lattice demonstrate a fractal energy spectrum and the existence of edge states. We acknowledge support from the ONR (award N00014-14-1-0805), the ARO and the PECASE program (award W911NF-14-1-0154), the AFOSR (award FA9550-12-1-0305), and the Alfred P. Sloan foundation (grant BR2013-110).
Andreas S. Kronfeld
2002-09-30
After reviewing some of the mathematical foundations and numerical difficulties facing lattice QCD, I review the status of several calculations relevant to experimental high-energy physics. The topics considered are moments of structure functions, which may prove relevant to search for new phenomena at the LHC, and several aspects of flavor physics, which are relevant to understanding CP and flavor violation.
Feng Haidong; Siegel, Warren
2006-08-15
We propose some new simplifying ingredients for Feynman diagrams that seem necessary for random lattice formulations of superstrings. In particular, half the fermionic variables appear only in particle loops (similarly to loop momenta), reducing the supersymmetry of the constituents of the type IIB superstring to N=1, as expected from their interpretation in the 1/N expansion as super Yang-Mills.
ERIC Educational Resources Information Center
Scott, Paul
2006-01-01
A "convex" polygon is one with no re-entrant angles. Alternatively one can use the standard convexity definition, asserting that for any two points of the convex polygon, the line segment joining them is contained completely within the polygon. In this article, the author provides a solution to a problem involving convex lattice polygons.
NASA Astrophysics Data System (ADS)
Schaich, David
2016-03-01
Lattice field theory provides a non-perturbative regularization of strongly interacting systems, which has proven crucial to the study of quantum chromodynamics among many other theories. Supersymmetry plays prominent roles in the study of physics beyond the standard model, both as an ingredient in model building and as a tool to improve our understanding of quantum field theory. Attempts to apply lattice techniques to supersymmetric field theories have a long history, but until recently these efforts have generally encountered insurmountable difficulties related to the interplay of supersymmetry with the lattice discretization of spacetime. In recent years these difficulties have been overcome for a class of theories that includes the particularly interesting case of maximally supersymmetric Yang-Mills (N = 4 SYM) in four dimensions, which is a cornerstone of AdS/CFT duality. In combination with computational advances this progress enables practical numerical investigations of N = 4 SYM on the lattice, which can address questions that are difficult or impossible to handle through perturbation theory, AdS/CFT duality, or the conformal bootstrap program. I will briefly review some of the new ideas underlying this recent progress, and present some results from ongoing large-scale numerical calculations, including comparisons with analytic predictions.
NASA Astrophysics Data System (ADS)
Weidner, Carrie; Yu, Hoon; Anderson, Dana
2015-05-01
This work introduces a method to perform interferometry using atoms trapped in an optical lattice. Starting at t = 0 with atoms in the ground state of a lattice potential V(x) =V0cos [ 2 kx + ϕ(t) ] , we show that it is possible to transform from one atomic wavefunction to another by a prescribed shaking of the lattice, i.e., by an appropriately tailored time-dependent phase shift ϕ(t) . In particular, the standard interferometer sequence of beam splitting, propagation, reflection, reverse propagation, and recombination can be achieved via a set of phase modulation operations {ϕj(t) } . Each ϕj(t) is determined using a learning algorithm, and the split-step method calculates the wavefunction dynamics. We have numerically demonstrated an interferometer in which the shaken wavefunctions match the target states to better than 1 % . We carried out learning using a genetic algorithm and optimal control techniques. The atoms remain trapped in the lattice throughout the full interferometer sequence. Thus, the approach may be suitable for use in an dynamic environment. In addition to the general principles, we discuss aspects of the experimental implementation. Supported by the Office of Naval Research (ONR) and Northrop Grumman.
Estimation of the standard entropies of some Am(III) and Cm(III) compounds
NASA Astrophysics Data System (ADS)
Konings, R. J. M.
2001-05-01
The standard entropies S°(298.15 K) of some actinide(III) compounds have been estimated using a semi-empirical method describing the total entropy as the sum of the lattice entropy Slat and the excess entropy Sexs. The validity of the applied approach has been verified for the iso-electronic lanthanide(III) compounds for which a good agreement with experimental values has been obtained. The present results for the actinide(III) compounds are compared to previous estimates. Significant differences have been found, in particular for the americium compounds.
Methods for forming group III-arsenide-nitride semiconductor materials
NASA Technical Reports Server (NTRS)
Major, Jo S. (Inventor); Welch, David F. (Inventor); Scifres, Donald R. (Inventor)
2002-01-01
Methods are disclosed for forming Group III-arsenide-nitride semiconductor materials. Group III elements are combined with group V elements, including at least nitrogen and arsenic, in concentrations chosen to lattice match commercially available crystalline substrates. Epitaxial growth of these III-V crystals results in direct bandgap materials, which can be used in applications such as light emitting diodes and lasers. Varying the concentrations of the elements in the III-V crystals varies the bandgaps, such that materials emitting light spanning the visible spectra, as well as mid-IR and near-UV emitters, can be created. Conversely, such material can be used to create devices that acquire light and convert the light to electricity, for applications such as full color photodetectors and solar energy collectors. The growth of the III-V crystals can be accomplished by growing thin layers of elements or compounds in sequences that result in the overall lattice match and bandgap desired.
NASA Astrophysics Data System (ADS)
Hsu, Hsiao-Ping; Nadler, Walder; Grassberger, Peter
2005-07-01
The scaling behavior of randomly branched polymers in a good solvent is studied in two to nine dimensions, modeled by lattice animals on simple hypercubic lattices. For the simulations, we use a biased sequential sampling algorithm with re-sampling, similar to the pruned-enriched Rosenbluth method (PERM) used extensively for linear polymers. We obtain high statistics of animals with up to several thousand sites in all dimension 2⩽d⩽9. The partition sum (number of different animals) and gyration radii are estimated. In all dimensions we verify the Parisi-Sourlas prediction, and we verify all exactly known critical exponents in dimensions 2, 3, 4, and ⩾8. In addition, we present the hitherto most precise estimates for growth constants in d⩾3. For clusters with one site attached to an attractive surface, we verify the superuniversality of the cross-over exponent at the adsorption transition predicted by Janssen and Lyssy.
Lattice Boltzmann morphodynamic model
NASA Astrophysics Data System (ADS)
Zhou, Jian Guo
2014-08-01
Morphological change due to sediment transport is a common natural phenomenon in real flows. It involves complex processes of erosion and deposition such as those along beaches and in river beds, imposing a strong strain on human beings. Studying and understanding morphodynamic evolution are essential to protect living environment. Although there are conventional numerical methods like finite difference method and finite volume method for forecast of morphological change by solving flow and morphodynamic equations, the methods are too complex/inefficient to be applied to a real large scale problem. To overcome this, a lattice Boltzmann method is developed to simulate morphological evolution under flows. It provides an alternative way of studying morphodynamics at the full advantages of the lattice Boltzmann methodology. The model is verified by applications to the evolution of one and two dimensional sand dunes under shallow water flows.
Gupta, R.
1998-12-31
The goal of the lectures on lattice QCD (LQCD) is to provide an overview of both the technical issues and the progress made so far in obtaining phenomenologically useful numbers. The lectures consist of three parts. The author`s charter is to provide an introduction to LQCD and outline the scope of LQCD calculations. In the second set of lectures, Guido Martinelli will discuss the progress they have made so far in obtaining results, and their impact on Standard Model phenomenology. Finally, Martin Luescher will discuss the topical subjects of chiral symmetry, improved formulation of lattice QCD, and the impact these improvements will have on the quality of results expected from the next generation of simulations.
Kronfeld, A.S.; Allison, I.F.; Aubin, C.; Bernard, C.; Davies, C.T.H.; DeTar, C.; Di Pierro, M.; Freeland, E.D.; Gottlieb, Steven; Gray, A.; Gregor, E.; Heller, U.M.; Hetrick, J.E.; El-Khadra, Aida X.; Levkova, L.; Mackenzie, P.B.; Maresca, F.; Menscher, D.; Nobes, M.; Okamoto, M.; Oktay, M.B.; /Fermilab /Glasgow U. /Columbia U. /Washington U., St. Louis /Utah U. /DePaul U. /Art Inst. of Chicago /Indiana U. /Ohio State U. /Arizona U. /APS, New York /U. Pacific, Stockton /Illinois U., Urbana /Cornell U., LEPP /Simon Fraser U. /UC, Santa Barbara
2005-09-01
In the past year, we calculated with lattice QCD three quantities that were unknown or poorly known. They are the q{sup 2} dependence of the form factor in semileptonic D {yields} K/{nu} decay, the decay constant of the D meson, and the mass of the B{sub c} meson. In this talk, we summarize these calculations, with emphasis on their (subsequent) confirmation by experiments.
Multipole plasmonic lattice solitons
Kou Yao; Ye Fangwei; Chen Xianfeng
2011-09-15
We theoretically demonstrate a variety of multipole plasmonic lattice solitons, including dipoles, quadrupoles, and necklaces, in two-dimensional metallic nanowire arrays with Kerr-type nonlinearities. Such solitons feature complex internal structures with an ultracompact mode size approaching or smaller than one wavelength. Their mode sizes and the stability characteristics are studied in detail within the framework of coupled mode theory. The conditions to form and stabilize these highly confined solitons are within the experimentally achievable range.
Nucleon Structure from Lattice QCD
David Richards
2007-09-05
Recent advances in lattice field theory, in computer technology and in chiral perturbation theory have enabled lattice QCD to emerge as a powerful quantitative tool in understanding hadron structure. I describe recent progress in the computation of the nucleon form factors and moments of parton distribution functions, before proceeding to describe lattice studies of the Generalized Parton Distributions (GPDs). In particular, I show how lattice studies of GPDs contribute to building a three-dimensional picture of the proton, I conclude by describing the prospects for studying the structure of resonances from lattice QCD.
Crystallographic Lattice Boltzmann Method.
Namburi, Manjusha; Krithivasan, Siddharth; Ansumali, Santosh
2016-01-01
Current approaches to Direct Numerical Simulation (DNS) are computationally quite expensive for most realistic scientific and engineering applications of Fluid Dynamics such as automobiles or atmospheric flows. The Lattice Boltzmann Method (LBM), with its simplified kinetic descriptions, has emerged as an important tool for simulating hydrodynamics. In a heterogeneous computing environment, it is often preferred due to its flexibility and better parallel scaling. However, direct simulation of realistic applications, without the use of turbulence models, remains a distant dream even with highly efficient methods such as LBM. In LBM, a fictitious lattice with suitable isotropy in the velocity space is considered to recover Navier-Stokes hydrodynamics in macroscopic limit. The same lattice is mapped onto a cartesian grid for spatial discretization of the kinetic equation. In this paper, we present an inverted argument of the LBM, by making spatial discretization as the central theme. We argue that the optimal spatial discretization for LBM is a Body Centered Cubic (BCC) arrangement of grid points. We illustrate an order-of-magnitude gain in efficiency for LBM and thus a significant progress towards feasibility of DNS for realistic flows. PMID:27251098
Crystallographic Lattice Boltzmann Method
Namburi, Manjusha; Krithivasan, Siddharth; Ansumali, Santosh
2016-01-01
Current approaches to Direct Numerical Simulation (DNS) are computationally quite expensive for most realistic scientific and engineering applications of Fluid Dynamics such as automobiles or atmospheric flows. The Lattice Boltzmann Method (LBM), with its simplified kinetic descriptions, has emerged as an important tool for simulating hydrodynamics. In a heterogeneous computing environment, it is often preferred due to its flexibility and better parallel scaling. However, direct simulation of realistic applications, without the use of turbulence models, remains a distant dream even with highly efficient methods such as LBM. In LBM, a fictitious lattice with suitable isotropy in the velocity space is considered to recover Navier-Stokes hydrodynamics in macroscopic limit. The same lattice is mapped onto a cartesian grid for spatial discretization of the kinetic equation. In this paper, we present an inverted argument of the LBM, by making spatial discretization as the central theme. We argue that the optimal spatial discretization for LBM is a Body Centered Cubic (BCC) arrangement of grid points. We illustrate an order-of-magnitude gain in efficiency for LBM and thus a significant progress towards feasibility of DNS for realistic flows. PMID:27251098
Crystallographic Lattice Boltzmann Method
NASA Astrophysics Data System (ADS)
Namburi, Manjusha; Krithivasan, Siddharth; Ansumali, Santosh
2016-06-01
Current approaches to Direct Numerical Simulation (DNS) are computationally quite expensive for most realistic scientific and engineering applications of Fluid Dynamics such as automobiles or atmospheric flows. The Lattice Boltzmann Method (LBM), with its simplified kinetic descriptions, has emerged as an important tool for simulating hydrodynamics. In a heterogeneous computing environment, it is often preferred due to its flexibility and better parallel scaling. However, direct simulation of realistic applications, without the use of turbulence models, remains a distant dream even with highly efficient methods such as LBM. In LBM, a fictitious lattice with suitable isotropy in the velocity space is considered to recover Navier-Stokes hydrodynamics in macroscopic limit. The same lattice is mapped onto a cartesian grid for spatial discretization of the kinetic equation. In this paper, we present an inverted argument of the LBM, by making spatial discretization as the central theme. We argue that the optimal spatial discretization for LBM is a Body Centered Cubic (BCC) arrangement of grid points. We illustrate an order-of-magnitude gain in efficiency for LBM and thus a significant progress towards feasibility of DNS for realistic flows.
Lattice QCD for parallel computers
NASA Astrophysics Data System (ADS)
Quadling, Henley Sean
Lattice QCD is an important tool in the investigation of Quantum Chromodynamics (QCD). This is particularly true at lower energies where traditional perturbative techniques fail, and where other non-perturbative theoretical efforts are not entirely satisfactory. Important features of QCD such as confinement and the masses of the low lying hadronic states have been demonstrated and calculated in lattice QCD simulations. In calculations such as these, non-lattice techniques in QCD have failed. However, despite the incredible advances in computer technology, a full solution of lattice QCD may still be in the too-distant future. Much effort is being expended in the search for ways to reduce the computational burden so that an adequate solution of lattice QCD is possible in the near future. There has been considerable progress in recent years, especially in the research of improved lattice actions. In this thesis, a new approach to lattice QCD algorithms is introduced, which results in very significant efficiency improvements. The new approach is explained in detail, evaluated and verified by comparing physics results with current lattice QCD simulations. The new sub-lattice layout methodology has been specifically designed for current and future hardware. Together with concurrent research into improved lattice actions and more efficient numerical algorithms, the very significant efficiency improvements demonstrated in this thesis can play an important role in allowing lattice QCD researchers access to much more realistic simulations. The techniques presented in this thesis also allow ambitious QCD simulations to be performed on cheap clusters of commodity computers.
Toward lattice fractional vector calculus
NASA Astrophysics Data System (ADS)
Tarasov, Vasily E.
2014-09-01
An analog of fractional vector calculus for physical lattice models is suggested. We use an approach based on the models of three-dimensional lattices with long-range inter-particle interactions. The lattice analogs of fractional partial derivatives are represented by kernels of lattice long-range interactions, where the Fourier series transformations of these kernels have a power-law form with respect to wave vector components. In the continuum limit, these lattice partial derivatives give derivatives of non-integer order with respect to coordinates. In the three-dimensional description of the non-local continuum, the fractional differential operators have the form of fractional partial derivatives of the Riesz type. As examples of the applications of the suggested lattice fractional vector calculus, we give lattice models with long-range interactions for the fractional Maxwell equations of non-local continuous media and for the fractional generalization of the Mindlin and Aifantis continuum models of gradient elasticity.
A Mechanical Lattice Aid for Crystallography Teaching.
ERIC Educational Resources Information Center
Amezcua-Lopez, J.; Cordero-Borboa, A. E.
1988-01-01
Introduces a 3-dimensional mechanical lattice with adjustable telescoping mechanisms. Discusses the crystalline state, the 14 Bravais lattices, operational principles of the mechanical lattice, construction methods, and demonstrations in classroom. Provides lattice diagrams, schemes of the lattice, and various pictures of the lattice. (YP)
Lattice-induced nonadiabatic frequency shifts in optical lattice clocks
Beloy, K.
2010-09-15
We consider the frequency shift in optical lattice clocks which arises from the coupling of the electronic motion to the atomic motion within the lattice. For the simplest of three-dimensional lattice geometries this coupling is shown to affect only clocks based on blue-detuned lattices. We have estimated the size of this shift for the prospective strontium lattice clock operating at the 390-nm blue-detuned magic wavelength. The resulting fractional frequency shift is found to be on the order of 10{sup -18} and is largely overshadowed by the electric quadrupole shift. For lattice clocks based on more complex geometries or other atomic systems, this shift could potentially be a limiting factor in clock accuracy.
Single identities for lattice theory and for weakly associative lattices
McCune, W.; Padmanabhan, R.
1995-03-13
We present a single identity for the variety of all lattices that is much simpler than those previously known to us. We also show that the variety of weakly associative lattices is one-based, and we present a generalized one-based theorem for subvarieties of weakly associative lattices that can be defined with absorption laws. The automated theorem-proving program OTTER was used in substantial way to obtain the results.
Matsuoka, H.
1985-01-01
The thermodynamic consequences of QCD are explored in the framework of lattice gauge theory. Attention is focused upon the nature of the chiral symmetry restoration transition at finite temperature and at finite baryon density, and possible strategies for identifying relevant thermodynamic phases are discussed. Some numerical results are presented on the chiral symmetry restoration in the SU(2) gauge theory at high baryon density. The results suggest that with T approx. = 110 MeV there is a second order restoration transition at the critical baryon density n/sub B//sup c/ approx. = 0.62 fm/sup -3/.
Rasmussen, S. |; Smith, J.R. |
1995-05-01
We present a new style of molecular dynamics and self-assembly simulation, the Lattice Polymer Automaton (LPA). In the LPA all interactions, including electromagnetic forces, are decomposed and communicated via propagating particles, {open_quotes}photons.{close_quotes} The monomer-monomer bondforces, the molecular excluded volume forces, the longer range intermolecular forces, and the polymer-solvent interactions may all be modeled with propagating particles. The LPA approach differs significantly from both of the standard approaches, Monte Carlo lattice methods and Molecular Dynamics simulations. On the one hand, the LPA provides more realism than Monte Carlo methods, because it produces a time series of configurations of a single molecule, rather than a set of causally unrelated samples from a distribution of configurations. The LPA can therefore be used directly to study dynamical properties; one can in fact watch polymers move in real time. On the other hand, the LPA is fully discrete, and therefore much simpler than traditional Molecular Dynamics models, which are continuous and operate on much shorter time scales. Due to this simplicity it is possible to simulate longer real time periods, which should enable the study of molecular self-organization on workstations supercomputers are not needed.
Nuclear Physics and Lattice QCD
Beane, Silas
2003-11-01
Impressive progress is currently being made in computing properties and interac- tions of the low-lying hadrons using lattice QCD. However, cost limitations will, for the foreseeable future, necessitate the use of quark masses, Mq, that are signif- icantly larger than those of nature, lattice spacings, a, that are not significantly smaller than the physical scale of interest, and lattice sizes, L, that are not sig- nificantly larger than the physical scale of interest. Extrapolations in the quark masses, lattice spacing and lattice volume are therefore required. The hierarchy of mass scales is: L 1 j Mq j â ºC j a 1 . The appropriate EFT for incorporating the light quark masses, the finite lattice spacing and the lattice size into hadronic observables is C-PT, which provides systematic expansions in the small parame- ters e m L, 1/ Lâ ºC, p/â ºC, Mq/â ºC and aâ ºC . The lattice introduces other unphysical scales as well. Lattice QCD quarks will increasingly be artificially separated
Quantum Gases in Optical Lattices
NASA Astrophysics Data System (ADS)
Barmettler, Peter; Kollath, Corinna
2015-09-01
The experimental realization of correlated quantum phases with ultracold gases in optical lattices and their theoretical understanding has witnessed remarkable progress during the last decade. In this review we introduce basic concepts and tools to describe the many-body physics of quantum gases in optical lattices. This includes the derivation of effective lattice Hamiltonians from first principles and an overview of the emerging quantum phases. Additionally, state-of-the-art numerical tools to quantitatively treat bosons or fermions on different lattices are introduced.
Elimination of spurious lattice fermion solutions and noncompact lattice QCD
Lee, T.D.
1997-09-22
It is well known that the Dirac equation on a discrete hyper-cubic lattice in D dimension has 2{sup D} degenerate solutions. The usual method of removing these spurious solutions encounters difficulties with chiral symmetry when the lattice spacing l {ne} 0, as exemplified by the persistent problem of the pion mass. On the other hand, we recall that in any crystal in nature, all the electrons do move in a lattice and satisfy the Dirac equation; yet there is not a single physical result that has ever been entangled with a spurious fermion solution. Therefore it should not be difficult to eliminate these unphysical elements. On a discrete lattice, particle hop from point to point, whereas in a real crystal the lattice structure in embedded in a continuum and electrons move continuously from lattice cell to lattice cell. In a discrete system, the lattice functions are defined only on individual points (or links as in the case of gauge fields). However, in a crystal the electron state vector is represented by the Bloch wave functions which are continuous functions in {rvec {gamma}}, and herein lies one of the essential differences.
Physical symmetry and lattice symmetry in the lattice Boltzmann method
Cao, N.; Chen, S.; Jin, S.; Martinez, D.
1997-01-01
The lattice Boltzmann method (LBM) is regarded as a specific finite difference discretization for the kinetic equation of the discrete velocity distribution function. We argue that for finite sets of discrete velocity models, such as LBM, the physical symmetry is necessary for obtaining the correct macroscopic Navier-Stokes equations. In contrast, the lattice symmetry and the Lagrangian nature of the scheme, which is often used in the lattice gas automaton method and the existing lattice Boltzmann methods and directly associated with the property of particle dynamics, is not necessary for recovering the correct macroscopic dynamics. By relaxing the lattice symmetry constraint and introducing other numerical discretization, one can also obtain correct hydrodynamics. In addition, numerical simulations for applications, such as nonuniform meshes and thermohydrodynamics can be easily carried out and numerical stability can be ensured by the Courant-Friedricks-Lewey condition and using the semi-implicit collision scheme. {copyright} {ital 1997} {ital The American Physical Society}
Optical Abelian lattice gauge theories
Tagliacozzo, L.; Celi, A.; Zamora, A.; Lewenstein, M.
2013-03-15
We discuss a general framework for the realization of a family of Abelian lattice gauge theories, i.e., link models or gauge magnets, in optical lattices. We analyze the properties of these models that make them suitable for quantum simulations. Within this class, we study in detail the phases of a U(1)-invariant lattice gauge theory in 2+1 dimensions, originally proposed by P. Orland. By using exact diagonalization, we extract the low-energy states for small lattices, up to 4 Multiplication-Sign 4. We confirm that the model has two phases, with the confined entangled one characterized by strings wrapping around the whole lattice. We explain how to study larger lattices by using either tensor network techniques or digital quantum simulations with Rydberg atoms loaded in optical lattices, where we discuss in detail a protocol for the preparation of the ground-state. We propose two key experimental tests that can be used as smoking gun of the proper implementation of a gauge theory in optical lattices. These tests consist in verifying the absence of spontaneous (gauge) symmetry breaking of the ground-state and the presence of charge confinement. We also comment on the relation between standard compact U(1) lattice gauge theory and the model considered in this paper. - Highlights: Black-Right-Pointing-Pointer We study the quantum simulation of dynamical gauge theories in optical lattices. Black-Right-Pointing-Pointer We focus on digital simulation of abelian lattice gauge theory. Black-Right-Pointing-Pointer We rediscover and discuss the puzzling phase diagram of gauge magnets. Black-Right-Pointing-Pointer We detail the protocol for time evolution and ground-state preparation in any phase. Black-Right-Pointing-Pointer We provide two experimental tests to validate gauge theory quantum simulators.
Silver(II) Oxide or Silver(I,III) Oxide?
ERIC Educational Resources Information Center
Tudela, David
2008-01-01
The often called silver peroxide and silver(II) oxide, AgO or Ag[subscript 2]O[subscript 2], is actually a mixed oxidation state silver(I,III) oxide. A thermochemical cycle, with lattice energies calculated within the "volume-based" thermodynamic approach, explain why the silver(I,III) oxide is more stable than the hypothetical silver(II) oxide.…
Excitonic surface lattice resonances
NASA Astrophysics Data System (ADS)
Humphrey, A. D.; Gentile, M. J.; Barnes, W. L.
2016-08-01
Electromagnetic resonances are important in controlling light at the nanoscale. The most studied such resonance is the surface plasmon resonance that is associated with metallic nanostructures. Here we explore an alternative resonance, the surface exciton-polariton resonance, one based on excitonic molecular materials. Our study is based on analytical and numerical modelling. We show that periodic arrays of suitable molecular nanoparticles may support surface lattice resonances that arise as a result of coherent interactions between the particles. Our results demonstrate that excitonic molecular materials are an interesting alternative to metals for nanophotonics; they offer the prospect of both fabrication based on supramolecular chemistry and optical functionality arising from the way the properties of such materials may be controlled with light.
Characterization of projection lattices of Hilbert spaces
Szambien, H.H.
1986-09-01
The classical lattices of projections of Hilbert spaces over the real, the complex or the quaternion number field are characterized among the totality of irreducible, complete, orthomodular, atomic lattices satisfying the covering property. To this end, so-called paratopological lattices are introduced, i.e, lattices carrying a topology that renders the lattice operations restrictedly continuous.
Advances in lattice gauge theory
Duke, D.W.; Owens, J.F.
1985-01-01
This book presents papers on advances in lattice gauge theory. Topics covered include fermion Monte Carlo algorithms, portrait of a proton, critical behavior in QCD, the standard Higgs-model on the lattice, analytic calculation of mass gaps, and simulation of discrete Euclidean quantum gravity.
Buckling modes in pantographic lattices
NASA Astrophysics Data System (ADS)
Giorgio, Ivan; Della Corte, Alessandro; dell'Isola, Francesco; Steigmann, David J.
2016-07-01
We study buckling patterns in pantographic sheets, regarded as two-dimensional continua consisting of lattices of continuously distributed fibers. The fibers are modeled as beams endowed with elastic resistance to stretching, shearing, bending and twist. Included in the theory is a non-standard elasticity due to geodesic bending of the fibers relative to the lattice surface. xml:lang="fr"
Introduction to lattice gauge theory
NASA Astrophysics Data System (ADS)
Gupta, R.
The lattice formulation of Quantum Field Theory (QFT) can be exploited in many ways. We can derive the lattice Feynman rules and carry out weak coupling perturbation expansions. The lattice then serves as a manifestly gauge invariant regularization scheme, albeit one that is more complicated than standard continuum schemes. Strong coupling expansions: these give us useful qualitative information, but unfortunately no hard numbers. The lattice theory is amenable to numerical simulations by which one calculates the long distance properties of a strongly interacting theory from first principles. The observables are measured as a function of the bare coupling g and a gauge invariant cut-off approx. = 1/alpha, where alpha is the lattice spacing. The continuum (physical) behavior is recovered in the limit alpha yields 0, at which point the lattice artifacts go to zero. This is the more powerful use of lattice formulation, so in these lectures the author focuses on setting up the theory for the purpose of numerical simulations to get hard numbers. The numerical techniques used in Lattice Gauge Theories have their roots in statistical mechanics, so it is important to develop an intuition for the interconnection between quantum mechanics and statistical mechanics.
Berg,J.S.
2008-02-21
I give a brief introduction to the purpose and goals of the EMMA experiment and describe how they will impact the design of the main EMMA ring. I then describe the mathematical model that is used to describe the EMMA lattice. Finally, I show how the different lattice configurations were obtained and list their parameters.
Nonlinear dust-lattice waves: a modified Toda lattice
Cramer, N. F.
2008-09-07
Charged dust grains in a plasma interact with a Coulomb potential, but also with an exponential component to the potential, due to Debye shielding in the background plasma. Here we investigate large-amplitude oscillations and waves in dust-lattices, employing techniques used in Toda lattice analysis. The lattice consists of a linear chain of particles, or a periodic ring as occurs in experimentally observed dust particle clusters. The particle motion has a triangular waveform, and chaotic motion for large amplitude motion of a grain.
Kenneth Wilson and Lattice QCD
NASA Astrophysics Data System (ADS)
Ukawa, Akira
2015-09-01
We discuss the physics and computation of lattice QCD, a space-time lattice formulation of quantum chromodynamics, and Kenneth Wilson's seminal role in its development. We start with the fundamental issue of confinement of quarks in the theory of the strong interactions, and discuss how lattice QCD provides a framework for understanding this phenomenon. A conceptual issue with lattice QCD is a conflict of space-time lattice with chiral symmetry of quarks. We discuss how this problem is resolved. Since lattice QCD is a non-linear quantum dynamical system with infinite degrees of freedom, quantities which are analytically calculable are limited. On the other hand, it provides an ideal case of massively parallel numerical computations. We review the long and distinguished history of parallel-architecture supercomputers designed and built for lattice QCD. We discuss algorithmic developments, in particular the difficulties posed by the fermionic nature of quarks, and their resolution. The triad of efforts toward better understanding of physics, better algorithms, and more powerful supercomputers have produced major breakthroughs in our understanding of the strong interactions. We review the salient results of this effort in understanding the hadron spectrum, the Cabibbo-Kobayashi-Maskawa matrix elements and CP violation, and quark-gluon plasma at high temperatures. We conclude with a brief summary and a future perspective.
Legless locomotion in lattices
NASA Astrophysics Data System (ADS)
Schiebel, Perrin; Goldman, Daniel I.
2014-11-01
Little is known about interactions between an animal body and complex terrestrial terrain like sand and boulders during legless, undulatory travel (e.g. snake locomotion). We study the locomotor performance of Mojave shovel-nosed snakes (Chionactisoccipitalis , ~ 35 cm long) using a simplified model of heterogeneous terrain: symmetric lattices of obstacles. To quantify performance we measure mean forward speed and slip angle, βs, defined as the angle between the instantaneous velocity and tangent vectors at each point on the body. We find that below a critical peg density the presence of granular media results in high speed (~ 60 cm/s), low average slip (βs ~6°) snake performance as compared to movement in the same peg densities on hard ground (~ 25 cm/s and βs ~15°). Above this peg density, performance on granular and hard substrates converges. Speed on granular media decreases with increasing peg density to that of the speed on hard ground, while speed on hard ground remains constant. Conversely, βs on hard ground trends toward that on granular media as obstacle density increases.
Localized structures in Kagome lattices
Saxena, Avadh B; Bishop, Alan R; Law, K J H; Kevrekidis, P G
2009-01-01
We investigate the existence and stability of gap vortices and multi-pole gap solitons in a Kagome lattice with a defocusing nonlinearity both in a discrete case and in a continuum one with periodic external modulation. In particular, predictions are made based on expansion around a simple and analytically tractable anti-continuum (zero coupling) limit. These predictions are then confirmed for a continuum model of an optically-induced Kagome lattice in a photorefractive crystal obtained by a continuous transformation of a honeycomb lattice.
Lattice QCD clusters at Fermilab
Holmgren, D.; Mackenzie, Paul B.; Singh, Anitoj; Simone, Jim; /Fermilab
2004-12-01
As part of the DOE SciDAC ''National Infrastructure for Lattice Gauge Computing'' project, Fermilab builds and operates production clusters for lattice QCD simulations. This paper will describe these clusters. The design of lattice QCD clusters requires careful attention to balancing memory bandwidth, floating point throughput, and network performance. We will discuss our investigations of various commodity processors, including Pentium 4E, Xeon, Opteron, and PPC970. We will also discuss our early experiences with the emerging Infiniband and PCI Express architectures. Finally, we will present our predictions and plans for future clusters.
Quantum vortices in optical lattices
Vignolo, P.; Fazio, R.; Tosi, M. P.
2007-08-15
A vortex in a superfluid gas inside an optical lattice can behave as a massive particle moving in a periodic potential and exhibiting quantum properties. In this paper we discuss these properties and show that the excitation of vortex dynamics in a two-dimensional lattice can lead to striking measurable changes in its dynamic response. It would be possible by means of Bragg spectroscopy to carry out the first direct measurement of the effective vortex mass. In addition, the experiments proposed here provide an alternative way to study the pinning to the underlying lattice and the dissipative damping.
Reliability analysis of interdependent lattices
NASA Astrophysics Data System (ADS)
Limiao, Zhang; Daqing, Li; Pengju, Qin; Bowen, Fu; Yinan, Jiang; Zio, Enrico; Rui, Kang
2016-06-01
Network reliability analysis has drawn much attention recently due to the risks of catastrophic damage in networked infrastructures. These infrastructures are dependent on each other as a result of various interactions. However, most of the reliability analyses of these interdependent networks do not consider spatial constraints, which are found important for robustness of infrastructures including power grid and transport systems. Here we study the reliability properties of interdependent lattices with different ranges of spatial constraints. Our study shows that interdependent lattices with strong spatial constraints are more resilient than interdependent Erdös-Rényi networks. There exists an intermediate range of spatial constraints, at which the interdependent lattices have minimal resilience.
Andreas S. Kronfeld
2003-11-05
This paper is a review of heavy quarks in lattice gauge theory, focusing on methodology. It includes a status report on some of the calculations that are relevant to heavy-quark spectroscopy and to flavor physics.
GMUGLE: A goal lattice constructor
NASA Astrophysics Data System (ADS)
Hintz, Kenneth J.
2001-08-01
Goal lattices are a method for ordering the goals of a system and associating with each goal the value of performing that goal in terms of how much it contributes to the accomplishment of the topmost goal of a system. This paper presents a progress report on the development of a web-based implementation of the George Mason University Goal Lattice Engine (GMUGLE). GMUGLE allows a user to interactively create goal lattices, add/delete goals, and specify their ordering relations through a web-based interface. The database portion automatically computes the GLB and LUB of pairs of goals which have been entered to form them into a lattice. Yet to be implemented is the code to input goal values, automatically apportion the values among included goals, and accrue value among the included goals.
Lattice Tube Model of Proteins
NASA Astrophysics Data System (ADS)
Banavar, Jayanth R.; Cieplak, Marek; Maritan, Amos
2004-11-01
We present a new lattice model for proteins that incorporates a tubelike anisotropy by introducing a preference for mutually parallel alignments in the conformations. The model is demonstrated to capture many aspects of real proteins.
Lattice QCD in rotating frames.
Yamamoto, Arata; Hirono, Yuji
2013-08-23
We formulate lattice QCD in rotating frames to study the physics of QCD matter under rotation. We construct the lattice QCD action with the rotational metric and apply it to the Monte Carlo simulation. As the first application, we calculate the angular momenta of gluons and quarks in the rotating QCD vacuum. This new framework is useful to analyze various rotation-related phenomena in QCD. PMID:24010426
Energy of infinite vortex lattices
Campbell, L.J.; Doria, M.M.; Kadtke, J.B.
1989-05-15
An expression is derived for the energy density of a lattice of point vortices (or other logarithmic objects) having an arbitrary number of vortices of arbitrary strengths in an arbitrary unit cell. The result is expressed in the form of a rapidly convergent series well suited for numerical evaluation. The effects of separately changing the shape and dimensions of the unit cell are shown for simple cases, and the energy of the triangular lattice is calculated as a function of slip displacement.
Mello Koch, Robert de; Mashile, Grant; Park, Nicholas
2010-05-15
In this article the anomalous dimension of a class of operators with a bare dimension of O(N) is studied. The operators considered are dual to excited states of a two giant graviton system. In the Yang-Mills theory they are described by restricted Schur polynomials, labeled with Young diagrams that have at most two columns. In a certain limit the dilatation operator looks like a lattice version of a second derivative, with the lattice emerging from the Young diagram itself.
Fully relativistic lattice Boltzmann algorithm
Romatschke, P.; Mendoza, M.; Succi, S.
2011-09-15
Starting from the Maxwell-Juettner equilibrium distribution, we develop a relativistic lattice Boltzmann (LB) algorithm capable of handling ultrarelativistic systems with flat, but expanding, spacetimes. The algorithm is validated through simulations of a quark-gluon plasma, yielding excellent agreement with hydrodynamic simulations. The present scheme opens the possibility of transferring the recognized computational advantages of lattice kinetic theory to the context of both weakly and ultrarelativistic systems.
Hadronic Resonances from Lattice QCD
Lichtl, Adam C.; Bulava, John; Morningstar, Colin; Edwards, Robert; Mathur, Nilmani; Richards, David; Fleming, George; Juge, K. Jimmy; Wallace, Stephen J.
2007-10-26
The determination of the pattern of hadronic resonances as predicted by Quantum Chromodynamics requires the use of non-perturbative techniques. Lattice QCD has emerged as the dominant tool for such calculations, and has produced many QCD predictions which can be directly compared to experiment. The concepts underlying lattice QCD are outlined, methods for calculating excited states are discussed, and results from an exploratory Nucleon and Delta baryon spectrum study are presented.
Transport in Sawtooth photonic lattices
NASA Astrophysics Data System (ADS)
Weimann, Steffen; Morales-Inostroza, Luis; Real, Bastián; Cantillano, Camilo; Szameit, Alexander; Vicencio, Rodrigo A.
2016-06-01
We investigate, theoretically and experimentally, a photonic realization of a Sawtooth lattice. This special lattice exhibits two spectral bands, with one of them experiencing a complete collapse to a highly degenerate flat band for a special set of inter-site coupling constants. We report the ob- servation of different transport regimes, including strong transport inhibition due to the appearance of the non-diffractive flat band. Moreover, we excite localized Shockley surfaces states, residing in the gap between the two linear bands.
Yamamoto, Arata
2016-07-29
We propose the lattice QCD calculation of the Berry phase, which is defined by the ground state of a single fermion. We perform the ground-state projection of a single-fermion propagator, construct the Berry link variable on a momentum-space lattice, and calculate the Berry phase. As the first application, the first Chern number of the (2+1)-dimensional Wilson fermion is calculated by the Monte Carlo simulation. PMID:27517766
NASA Astrophysics Data System (ADS)
Holmgren, D. J.
2005-03-01
In the last several years, tightly coupled PC clusters have become widely applied, cost effective resources for lattice gauge computations. This paper discusses the practice of building such clusters, in particular balanced design requirements. I review and quantify the improvements over time of key performance parameters and overall price to performance ratio. Applying these trends and technology forecasts given by computer equipment manufacturers, I predict the range of price to performance for lattice codes expected in the next several years.
DeGrand, T.
1997-06-01
These lectures provide an introduction to lattice methods for nonperturbative studies of Quantum Chromodynamics. Lecture 1: Basic techniques for QCD and results for hadron spectroscopy using the simplest discretizations; lecture 2: Improved actions--what they are and how well they work; lecture 3: SLAC physics from the lattice-structure functions, the mass of the glueball, heavy quarks and {alpha}{sub s} (M{sub z}), and B-{anti B} mixing. 67 refs., 36 figs.
Hadronic Resonances from Lattice QCD
John Bulava; Robert Edwards; George Fleming; K. Jimmy Juge; Adam C. Lichtl; Nilmani Mathur; Colin Morningstar; David Richards; Stephen J. Wallace
2007-06-16
The determination of the pattern of hadronic resonances as predicted by Quantum Chromodynamics requires the use of non-perturbative techniques. Lattice QCD has emerged as the dominant tool for such calculations, and has produced many QCD predictions which can be directly compared to experiment. The concepts underlying lattice QCD are outlined, methods for calculating excited states are discussed, and results from an exploratory Nucleon and Delta baryon spectrum study are presented.
Optimal lattice-structured materials
Messner, Mark C.
2016-07-09
This paper describes a method for optimizing the mesostructure of lattice-structured materials. These materials are periodic arrays of slender members resembling efficient, lightweight macroscale structures like bridges and frame buildings. Current additive manufacturing technologies can assemble lattice structures with length scales ranging from nanometers to millimeters. Previous work demonstrates that lattice materials have excellent stiffness- and strength-to-weight scaling, outperforming natural materials. However, there are currently no methods for producing optimal mesostructures that consider the full space of possible 3D lattice topologies. The inverse homogenization approach for optimizing the periodic structure of lattice materials requires a parameterized, homogenized material model describingmore » the response of an arbitrary structure. This work develops such a model, starting with a method for describing the long-wavelength, macroscale deformation of an arbitrary lattice. The work combines the homogenized model with a parameterized description of the total design space to generate a parameterized model. Finally, the work describes an optimization method capable of producing optimal mesostructures. Several examples demonstrate the optimization method. One of these examples produces an elastically isotropic, maximally stiff structure, here called the isotruss, that arguably outperforms the anisotropic octet truss topology.« less
A search for good lattice rules based on the reciprocal lattice generator matrix
Lyness, J.N.; Newman, W.
1989-01-01
The search for cost-effective lattice rules is a time-consuming and difficult process. After a brief overview of some of the lattice theory relevant to these rules, a new approach to this search is suggested. This approach is based on a classification of lattice rules using the upper triangular lattice form'' of the reciprocal lattice generator matrix. 18 refs., 1 tab.
Diluted magnetic III-V semiconductors
NASA Astrophysics Data System (ADS)
Munekata, H.; Ohno, H.; von Molnar, S.; Segmüller, Armin; Chang, L. L.; Esaki, L.
1989-10-01
A new diluted magnetic III-V semiconductor of In1-xMnxAs (x<=0.18) has been produced by molecular-beam epitaxy. Films grown at 300 °C are predominantly ferromagnetic and their properties suggest the presence of MnAs clusters. Films grown 200 °C, however, are predominantly paramagnetic, and the lattice constant decreases with increasing Mn composition; both are indicative of the formation of a homogeneous alloy. These films have n-type conductivity and reduced band gaps.
Lattice Boltzmann method for the Saint-Venant equations
NASA Astrophysics Data System (ADS)
Liu, Haifei; Wang, Hongda; Liu, Shu; Hu, Changwei; Ding, Yu; Zhang, Jie
2015-05-01
The Saint-Venant equations represent the hydrodynamic principles of unsteady flows in open channel network through a set of non-linear partial differential equations. In this paper, a new lattice Boltzmann approach to solving the one-dimensional Saint-Venant equations (LABSVE) is developed, demonstrating the variation of discharge and sectional area with external forces, such as bed slope and bed friction. Our research recovers the Saint-Venant equations through deducing the Chapman-Enskog expansion on the lattice Boltzmann equation, which is a mesoscopic technique, bridging the molecular movement and macroscopic physical variables. It is also a fully explicit process, providing simplicity for programming. The model is verified by three benchmark tests: (i) a one-dimensional subcritical gradient flow; (ii) a dam-break wave flow; (iii) a flood event on the Yongding River. The results showed the accuracy of the proposed method and its good applicability in solving Saint-Venant problems.
Algebraic Lattices in QFT Renormalization
NASA Astrophysics Data System (ADS)
Borinsky, Michael
2016-04-01
The structure of overlapping subdivergences, which appear in the perturbative expansions of quantum field theory, is analyzed using algebraic lattice theory. It is shown that for specific QFTs the sets of subdivergences of Feynman diagrams form algebraic lattices. This class of QFTs includes the standard model. In kinematic renormalization schemes, in which tadpole diagrams vanish, these lattices are semimodular. This implies that the Hopf algebra of Feynman diagrams is graded by the coradical degree or equivalently that every maximal forest has the same length in the scope of BPHZ renormalization. As an application of this framework, a formula for the counter terms in zero-dimensional QFT is given together with some examples of the enumeration of primitive or skeleton diagrams.
Madelung energy of Yukawa lattices.
Pereira, P C N; Apolinario, S W S
2012-10-01
We propose a method to obtain an approximate closed form expression for the Madelung energy (ME) of Yukawa lattices. Such a method is applied for lattices of different topologies and dimensions. The obtained Madelung energies have a satisfactory accuracy for all ranges of the screening parameter κ of the Yukawa potential, and it becomes exact in the asymptotic limits κ→0 and κ→+∞. For instance, for the triangular lattice, the maximum relative error of the ME given by the method is about 0.0047. Also, satisfactory results are obtained for the one-component plasma limit. The Madelung constants of the two-dimensional hexagonal BN and square NaCl and the three-dimensional cubic NaCl crystals are estimated with a relative error of 0.004, 0.006, and 0.03, respectively. Finally, different ways to improve the method are presented and discussed. PMID:23214705
Lattice QCD Beyond Ground States
Huey-Wen Lin; Saul D. Cohen
2007-09-11
In this work, we apply black box methods (methods not requiring input) to find excited-state energies. A variety of such methods for lattice QCD were introduced at the 3rd iteration of the numerical workshop series. We first review a selection of approaches that have been used in lattice calculations to determine multiple energy states: multiple correlator fits, the variational method and Bayesian fitting. In the second half, we will focus on a black box method, the multi-effective mass. We demonstrate the approach on a toy model, as well as on real lattice data, extracting multiple states from single correlators. Without complicated operator construction or specialized fitting programs, the black box method shows good consistency with the traditional approaches.
Lattice Structures For Aerospace Applications
NASA Astrophysics Data System (ADS)
Del Olmo, E.; Grande, E.; Samartin, C. R.; Bezdenejnykh, M.; Torres, J.; Blanco, N.; Frovel, M.; Canas, J.
2012-07-01
The way of mass reduction improving performances in the aerospace structures is a constant and relevant challenge in the space business. The designs, materials and manufacturing processes are permanently in evolution to explore and get mass optimization solutions at low cost. In the framework of ICARO project, EADS CASA ESPACIO (ECE) has designed, manufactured and tested a technology demonstrator which shows that lattice type of grid structures is a promising weight saving solution for replacing some traditional metallic and composite structures for space applications. A virtual testing methodology was used in order to support the design of a high modulus CFRP cylindrical lattice technology demonstrator. The manufacturing process, based on composite Automatic Fiber Placement (AFP) technology developed by ECE, allows obtaining high quality low weight lattice structures potentially applicable to a wide range of aerospace structures. Launcher payload adaptors, satellite platforms, antenna towers or instrument supports are some promising candidates.
Algebraic Lattices in QFT Renormalization
NASA Astrophysics Data System (ADS)
Borinsky, Michael
2016-07-01
The structure of overlapping subdivergences, which appear in the perturbative expansions of quantum field theory, is analyzed using algebraic lattice theory. It is shown that for specific QFTs the sets of subdivergences of Feynman diagrams form algebraic lattices. This class of QFTs includes the standard model. In kinematic renormalization schemes, in which tadpole diagrams vanish, these lattices are semimodular. This implies that the Hopf algebra of Feynman diagrams is graded by the coradical degree or equivalently that every maximal forest has the same length in the scope of BPHZ renormalization. As an application of this framework, a formula for the counter terms in zero-dimensional QFT is given together with some examples of the enumeration of primitive or skeleton diagrams.
K. Orginos
2011-12-01
In this talk I am reviewing recent calculations of properties of multi-hadron systems in lattice QCD. In particular, I am reviewing results of elastic scattering phase shifts in meson-meson, meson-baryon and baryon-baryon systems, as well as discussing results indicating possible existence of bound states in two baryon systems. Finally, calculations of properties of systems with more than two hadrons are presented.
Nucleon Structure from Lattice QCD
Haegler, Philipp
2011-10-24
Hadron structure calculations in lattice QCD have seen substantial progress during recent years. We illustrate the achievements that have been made by discussing latest lattice results for a limited number of important observables related to nucleon form factors and generalized parton distributions. A particular focus is placed on the decomposition of the nucleon spin 1/2 in terms of quark spin and orbital angular momentum contributions. Results and limitations of the necessary chiral extrapolations based on ChPT will be briefly discussed.
Lattice QCD and Nuclear Physics
Konstantinos Orginos
2007-03-01
A steady stream of developments in Lattice QCD have made it possible today to begin to address the question of how nuclear physics emerges from the underlying theory of strong interactions. Central role in this understanding play both the effective field theory description of nuclear forces and the ability to perform accurate non-perturbative calculations in lo w energy QCD. Here I present some recent results that attempt to extract important low energy constants of the effective field theory of nuclear forces from lattice QCD.
Machines for lattice gauge theory
Mackenzie, P.B.
1989-05-01
The most promising approach to the solution of the theory of strong interactions is large scale numerical simulation using the techniques of lattice gauge theory. At the present time, computing requirements for convincing calculations of the properties of hadrons exceed the capabilities of even the most powerful commercial supercomputers. This has led to the development of massively parallel computers dedicated to lattice gauge theory. This talk will discuss the computing requirements behind these machines, and general features of the components and architectures of the half dozen major projects now in existence. 20 refs., 1 fig.
VARIABLE MOMENTUM COMPACTION LATTICE STUDIES.
KRAMER,S.; MURPHY,J.B.
1999-03-29
The VUV storage ring at the National Synchrotron Light Source was used to study the impact of changes in the momentum compaction factors over a large range from positive to negative values. Changes in bunch length and synchrotron tune were measured versus current and RF parameters for these different lattices. By controlling both the first and second-order momentum compaction factors, a lattice was developed in which a pair of alpha buckets was created within the energy aperture of the vacuum chamber and beam was stored simultaneously in both buckets.
Nuclear Physics from Lattice QCD
William Detmold, Silas Beane, Konstantinos Orginos, Martin Savage
2011-01-01
We review recent progress toward establishing lattice Quantum Chromodynamics as a predictive calculational framework for nuclear physics. A survey of the current techniques that are used to extract low-energy hadronic scattering amplitudes and interactions is followed by a review of recent two-body and few-body calculations by the NPLQCD collaboration and others. An outline of the nuclear physics that is expected to be accomplished with Lattice QCD in the next decade, along with estimates of the required computational resources, is presented.
Methods for forming group III-V arsenide-nitride semiconductor materials
NASA Technical Reports Server (NTRS)
Major, Jo S. (Inventor); Welch, David F. (Inventor); Scifres, Donald R. (Inventor)
2000-01-01
Methods are disclosed for forming Group III--arsenide-nitride semiconductor materials. Group III elements are combined with group V elements, including at least nitrogen and arsenic, in concentrations chosen to lattice match commercially available crystalline substrates. Epitaxial growth of these III-V crystals results in direct bandgap materials, which can be used in applications such as light emitting diodes and lasers. Varying the concentrations of the elements in the III-V crystals varies the bandgaps, such that materials emitting light spanning the visible spectra, as well as mid-IR and near-UV emitters, can be created. Conversely, such material can be used to create devices that acquire light and convert the light to electricity, for applications such as full color photodetectors and solar energy collectors. The growth of the III-V crystals can be accomplished by growing thin layers of elements or compounds in sequences that result in the overall lattice match and bandgap desired.
Progress in lattice gauge theory
Creutz, M.
1983-01-01
These lectures first provide an overview of the current status of lattice gauge theory calculations. They then review some technical points on group integration, gauge fixing, and order parameters. Various Monte Carlo algorithms are discussed. Finally, alternatives to the Wilson action are considered in the context of universality for the continuum limit. 41 references.
Triangles in a Lattice Parabola.
ERIC Educational Resources Information Center
Sastry, K. R. S.
1991-01-01
Discussed are properties possessed by polygons inscribed in the lattice parabola y=x, including the area of a triangle, triangles of minimum area, conditions for right triangles, triangles whose area is the cube of an integer, and implications of Pick's Theorem. Further directions to pursue are suggested. (MDH)
Nonequilibrium model on Archimedean lattices
NASA Astrophysics Data System (ADS)
Lima, F.
2014-03-01
On (4, 6, 12) and (4, 82) Archimedean lattices, the critical properties of the majority-vote model are considered and studied using the Glauber transition rate proposed by Kwak et al. [Kwak et al., Phys. Rev. E, 75, 061110 (2007)] rather than the traditional majority-vote with noise [Oliveira, J. Stat. Phys. 66, 273 (1992)]. We obtain T c and the critical exponents for this Glauber rate from extensive Monte Carlo studies and finite size scaling. The calculated values of the critical temperatures and Binder cumulant are T c = 0.651(3) and U 4* = 0.612(5), and T c = 0.667(2) and U 4* = 0.613(5), for (4, 6, 12) and (4, 82) lattices respectively, while the exponent (ratios) β/ν, γ/ν and 1/ν are respectively: 0.105(8), 1.48(11) and 1.16(5) for (4, 6, 12); and 0.113(2), 1.60(4) and 0.84(6) for (4, 82) lattices. The usual Ising model and the majority-vote model on previously studied regular lattices or complex networks differ from our new results.
Nonequilibrium model on Archimedean lattices
NASA Astrophysics Data System (ADS)
Lima, F. Welington S.
2014-03-01
On (4, 6, 12) and (4, 82) Archimedean lattices, the critical properties of the majority-vote model are considered and studied using the Glauber transition rate proposed by Kwak et al. [Kwak et al., Phys. Rev. E, 75, 061110 (2007)] rather than the traditional majority-vote with noise [Oliveira, J. Stat. Phys. 66, 273 (1992)]. We obtain T c and the critical exponents for this Glauber rate from extensive Monte Carlo studies and finite size scaling. The calculated values of the critical temperatures and Binder cumulant are T c = 0.651(3) and U {4/*} = 0.612(5), and T c = 0.667(2) and U {4/*} = 0.613(5), for (4, 6, 12) and (4, 82) lattices respectively, while the exponent (ratios) β/ν, γ/ν and 1/ ν are respectively: 0.105(8), 1.48(11) and 1.16(5) for (4, 6, 12); and 0.113(2), 1.60(4) and 0.84(6) for (4, 82) lattices. The usual Ising model and the majority-vote model on previously studied regular lattices or complex networks differ from our new results.
Microparticle manipulation in optical lattices
NASA Astrophysics Data System (ADS)
Mu, Weiqiang
With the interference of several coherent beams, a periodical potential is produced for the particles trapped inside. The theoretical calculations show that the optical force applied on the particle in such optical lattice is in sinusoidal form. The force amplitudes vary greatly depending on the ratio of the particle size to the spacing of the optical lattice. A setup is constructed to demonstrate this dependence with two different methods: equipartition theorem and hydrodynamic-drag method. Based on this size dependence we develop an approach that allows tunable, size-dependent force selection of a subset of particles from an ensemble containing mixed particles. Combining a universal constant force with the sinusoidal optical force, a tilted washboard potential can be formed for the trapped particle. The diffusion of a particle over the barrier in this tilted washboard potential is briefly discussed. When the washboard potential oscillates, some interesting phenomena will happen: at high oscillation frequency, the particle's movement depends only on the oscillating amplitude; at low frequency, there are some combinations of the oscillation frequency and amplitude that induce the enhanced movement of the particle. This enhancement is first experimentally demonstrated with our setup. By implanting a single laser tweezers into the interferometric optical tweezers, we succeed in dynamically assembling designer colloidal lattices on the background of the interferometric optical tweezers. This new technique provides a flexible tool to design 2-d colloidal lattices.
Lattice QCD in Background Fields
William Detmold, Brian Tiburzi, Andre Walker-Loud
2009-06-01
Electromagnetic properties of hadrons can be computed by lattice simulations of QCD in background fields. We demonstrate new techniques for the investigation of charged hadron properties in electric fields. Our current calculations employ large electric fields, motivating us to analyze chiral dynamics in strong QED backgrounds, and subsequently uncover surprising non-perturbative effects present at finite volume.
Experimenting with Langevin lattice QCD
Gavai, R.V.; Potvin, J.; Sanielevici, S.
1987-05-01
We report on the status of our investigations of the effects of systematic errors upon the practical merits of Langevin updating in full lattice QCD. We formulate some rules for the safe use of this updating procedure and some observations on problems which may be common to all approximate fermion algorithms.
Simple theories of complex lattices
NASA Astrophysics Data System (ADS)
Peyrard, Michel
1998-11-01
While the theory of solitons has been very successful for continuous systems, very few nonlinear discrete lattices are amenable to an exact analytical treatment. In these “complex lattices” discreteness can be hostile to the solitons, preventing them to move due to the lack of translational invariance or even to exist as localized excitations. On the other hand, lattice discreteness can sometimes be very helpful. It can stabilize solutions that otherwise would split apart as in the discrete sine-Gordon lattice, or even allow the existence of localized oscillatory modes as exact solutions in systems where they would decay in the continuum limit. It is interesting that many of these phenomena can be understood qualitatively, and sometimes quantitatively, with very simple theories that rely on the usual concepts of linear wave propagation, resonances, linear stability of waves, for instance. There are, however, phenomena specific to discrete nonlinear lattices which allow the build up of large amplitude localized excitations, sometimes out of thermal fluctuations, which are more resistant to simple approaches and could deserve further interest because they may be relevant for various physical systems.
Hadronic Interactions from Lattice QCD
Konstantinos Orginos
2006-03-19
In this talk I discuss a few recent results on lattice calculations of scattering lengths in hadronic processes. In particular, I present the scattering length of the pion-pion scattering in the I=2 channel and the nucleon-nucleon {sup 1}S{sub 0} channel and {sup 3}S{sub 1}-{sup 3}D{sub 1} coupled channels.
Orbital optical lattices with bosons
NASA Astrophysics Data System (ADS)
Kock, T.; Hippler, C.; Ewerbeck, A.; Hemmerich, A.
2016-02-01
This article provides a synopsis of our recent experimental work exploring Bose-Einstein condensation in metastable higher Bloch bands of optical lattices. Bipartite lattice geometries have allowed us to implement appropriate band structures, which meet three basic requirements: the existence of metastable excited states sufficiently protected from collisional band relaxation, a mechanism to excite the atoms initially prepared in the lowest band with moderate entropy increase, and the possibility of cross-dimensional tunneling dynamics, necessary to establish coherence along all lattice axes. A variety of bands can be selectively populated and a subsequent thermalization process leads to the formation of a condensate in the lowest energy state of the chosen band. As examples the 2nd, 4th and 7th bands in a bipartite square lattice are discussed. The geometry of the 2nd and 7th bands can be tuned such that two inequivalent energetically degenerate energy minima arise at the X ±-points at the edge of the 1st Brillouin zone. In this case even a small interaction energy is sufficient to lock the phase between the two condensation points such that a complex-valued chiral superfluid order parameter can emerge, which breaks time reversal symmetry. In the 4th band a condensate can be formed at the Γ-point in the center of the 1st Brillouin zone, which can be used to explore topologically protected band touching points. The new techniques to access orbital degrees of freedom in higher bands greatly extend the class of many-body scenarios that can be explored with bosons in optical lattices.
The structure of a moving vortex lattice
Braun, D.W.; Crabtree, G.W.; Kaper, H.G.; Leaf, G.K.; Levine, D.M.; Vinokur, V.M.; Koshelev, A.E.
1995-11-01
Numerical solutions of the time-dependent Ginzburg-Landau equations show a new mechanism for plastic motion of a driven vortex lattice in a clean superconductor. The mechanism, which involves the creation of a defect superstructure, is intrinsic to the moving vortex lattice and is independent of bulk pinning. Other structural features found in the solutions include a reorientation of the vortex lattice and a gradual healing of lattice defects under the influence of a transport current.
Lattice dynamics and lattice thermal conductivity of thorium dicarbide
NASA Astrophysics Data System (ADS)
Liao, Zongmeng; Huai, Ping; Qiu, Wujie; Ke, Xuezhi; Zhang, Wenqing; Zhu, Zhiyuan
2014-11-01
The elastic and thermodynamic properties of ThC2 with a monoclinic symmetry have been studied by means of density functional theory and direct force-constant method. The calculated properties including the thermal expansion, the heat capacity and the elastic constants are in a good agreement with experiment. Our results show that the vibrational property of the C2 dimer in ThC2 is similar to that of a free standing C2 dimer. This indicates that the C2 dimer in ThC2 is not strongly bonded to Th atoms. The lattice thermal conductivity for ThC2 was calculated by means of the Debye-Callaway model. As a comparison, the conductivity of ThC was also calculated. Our results show that the ThC and ThC2 contributions of the lattice thermal conductivity to the total conductivity are 29% and 17%, respectively.
ERIC Educational Resources Information Center
North Carolina State Dept. of Public Education, Raleigh.
SUPERSTARS III is a K-8 program designed as an enrichment opportunity for self-directed learners in mathematics. The basic purpose of SUPERSTARS III is to provide the extra challenge that self-motivated students need in mathematics and to do so in a structured, long-term program that does not impinge on the normal classroom routine or the…
ERIC Educational Resources Information Center
Envirometrics, Inc., Washington, DC.
CITY III is a computer-assisted simulation game in which participants make decisions affecting the economic, governmental, and social conditions of a simulated urban area. In CITY III, the computer stores all the relevant statistics for the area, updates data when changes are made, and prints out yearly reports. The computer also simulates…
ERIC Educational Resources Information Center
Envirometrics, Inc., Washington, DC.
CITY III is a computer-assisted simulation game of an urban system involving player operation of and interaction with economic, social, and government components. The role of operator in the game is to take the handwritten inputs (decisions) from the CITY III participants, process them, and return output which initiates the next round of…
III-V aresenide-nitride semiconductor materials and devices
NASA Technical Reports Server (NTRS)
Major, Jo S. (Inventor); Welch, David F. (Inventor); Scifres, Donald R. (Inventor)
1997-01-01
III-V arsenide-nitride semiconductor crystals, methods for producing such crystals and devices employing such crystals. Group III elements are combined with group V elements, including at least nitrogen and arsenic, in concentrations chosen to lattice match commercially available crystalline substrates. Epitaxial growth of these III-V crystals results in direct bandgap materials, which can be used in applications such as light emitting diodes and lasers. Varying the concentrations of the elements in the III-V crystals varies the bandgaps, such that materials emitting light spanning the visible spectra, as well as mid-IR and near-UV emitters, can be created. Conversely, such material can be used to create devices that acquire light and convert the light to electricity, for applications such as full color photodetectors and solar energy collectors. The growth of the III-V crystals can be accomplished by growing thin layers of elements or compounds in sequences that result in the overall lattice match and bandgap desired.
The CKM Matrix from Lattice QCD
Mackenzie, Paul B.; /Fermilab
2009-07-01
Lattice QCD plays an essential role in testing and determining the parameters of the CKM theory of flavor mixing and CP violation. Very high precisions are required for lattice calculations analyzing CKM data; I discuss the prospects for achieving them. Lattice calculations will also play a role in investigating flavor mixing and CP violation beyond the Standard Model.
Lattice gaugefixing and other optics in lattice gauge theory
Yee, Ken.
1992-06-01
We present results from four projects. In the first, quark and gluon propagators and effective masses and {Delta}I = 1/2 Rule operator matching coefficients are computed numerically in gaugefixed lattice QCD. In the second, the same quantities are evaluated analytically in the strong coupling, N {yields} {infinity} limit. In the third project, the Schwinger model is studied in covariant gauges, where we show that the effective electron mass varies with the gauge parameter and that longitudinal gaugefixing ambiguities affect operator product expansion coefficients (analogous to {Delta}I = 1/2 Rule matching coefficients) determined by matching gauge variant matrix elements. However, we find that matching coefficients even if shifted by the unphysical modes are {xi} invariant. In the fourth project, we show that the strong coupling parallelogram lattice Schwinger model as a different thermodynamic limit than the weak coupling continuum limit. As a function of lattice skewness angle these models span the {Delta} = {minus}1 critical line of 6-vertex models which, in turn, have been identified as c = 1 conformal field theories.
Growth of III-Nitrides by molecular beam epitaxy
NASA Astrophysics Data System (ADS)
Tang, Liang
Nitride compound materials are highly desirable for optoelectronic and power device applications due to their unique combinations of material properties. However due to the large lattice mismatches between AlN and GaN(2.5%), and between InN and GaN(11%), growth of nitride devices which contains lattice mismatched multiple quantum well (MQW) structures remains a challenge. In this work the growth of III-Nitride by the MBE method is investigated, covering the growth of AlGaN/GaN Resonant tunneling Diode, the growth of In0.18 Al0.82N that is lattice matched to GaN, and the fabrication of free standing GaN nanomembranes
Lattice thermal expansion for normal tetrahedral compound semiconductors
Omar, M.S. . E-mail: dr_m_s_omar@yahoo.com
2007-02-15
The cubic root of the deviation of the lattice thermal expansion from that of the expected value of diamond for group IV semiconductors, binary compounds of III-V and II-VI, as well as several ternary compounds from groups I-III-VI{sub 2}, II-IV-V{sub 2} and I-IV{sub 2}V{sub 3} semiconductors versus their bonding length are given straight lines. Their slopes were found to be 0.0256, 0.0210, 0.0170, 0.0259, 0.0196, and 0.02840 for the groups above, respectively. Depending on the valence electrons of the elements forming these groups, a formula was found to correlate all the values of the slopes mentioned above to that of group IV. This new formula which depends on the melting point and the bonding length as well as the number of valence electrons for the elements forming the compounds, will gives best calculated values for lattice thermal expansion for all compounds forming the groups mentioned above. An empirical relation is also found between the mean ionicity of the compounds forming the groups and their slopes mentioned above and that gave the mean ionicity for the compound CuGe{sub 2}P{sub 3} in the range of 0.442.
Dru Renner
2012-04-01
Precision computation of hadronic physics with lattice QCD is becoming feasible. The last decade has seen precent-level calculations of many simple properties of mesons, and the last few years have seen calculations of baryon masses, including the nucleon mass, accurate to a few percent. As computational power increases and algorithms advance, the precise calculation of a variety of more demanding hadronic properties will become realistic. With this in mind, I discuss the current lattice QCD calculations of generalized parton distributions with an emphasis on the prospects for well-controlled calculations for these observables as well. I will do this by way of several examples: the pion and nucleon form factors and moments of the nucleon parton and generalized-parton distributions.
Lattice Simulations and Infrared Conformality
Appelquist, Thomas; Fleming, George T.; Lin, Meifeng; Neil, Ethan T.; Schaich, David A
2011-09-01
We examine several recent lattice-simulation data sets, asking whether they are consistent with infrared conformality. We observe, in particular, that for an SU(3) gauge theory with 12 Dirac fermions in the fundamental representation, recent simulation data can be described assuming infrared conformality. Lattice simulations include a fermion mass m which is then extrapolated to zero, and we note that this data can be fit by a small-m expansion, allowing a controlled extrapolation. We also note that the conformal hypothesis does not work well for two theories that are known or expected to be confining and chirally broken, and that itmore » does work well for another theory expected to be infrared conformal.« less
Entropy favours open colloidal lattices
NASA Astrophysics Data System (ADS)
Mao, Xiaoming; Chen, Qian; Granick, Steve
2013-03-01
Burgeoning experimental and simulation activity seeks to understand the existence of self-assembled colloidal structures that are not close-packed. Here we describe an analytical theory based on lattice dynamics and supported by experiments that reveals the fundamental role entropy can play in stabilizing open lattices. The entropy we consider is associated with the rotational and vibrational modes unique to colloids interacting through extended attractive patches. The theory makes predictions of the implied temperature, pressure and patch-size dependence of the phase diagram of open and close-packed structures. More generally, it provides guidance for the conditions at which targeted patchy colloidal assemblies in two and three dimensions are stable, thus overcoming the difficulty in exploring by experiment or simulation the full range of conceivable parameters.
LATTICE QCD AT FINITE DENSITY.
SCHMIDT, C.
2006-07-23
I discuss different approaches to finite density lattice QCD. In particular, I focus on the structure of the phase diagram and discuss attempts to determine the location of the critical end-point. Recent results on the transition line as function of the chemical potential (T{sub c}({mu}{sub q})) are reviewed. Along the transition line, hadronic fluctuations have been calculated; which can be used to characterize properties of the Quark Gluon plasma and eventually can also help to identify the location of the critical end-point in the QCD phase diagram on the lattice and in heavy ion experiments. Furthermore, I comment on the structure of the phase diagram at large {mu}{sub q}.
Lattice splitting under intermittent flows
NASA Astrophysics Data System (ADS)
Schläpfer, Markus; Trantopoulos, Konstantinos
2010-05-01
We study the splitting of regular square lattices subject to stochastic intermittent flows. Various flow patterns are produced by different groupings of the nodes, based on their random alternation between two possible states. The resulting flows on the lattices decrease with the number of groups according to a power law. By Monte Carlo simulations we reveal how the time span until the occurrence of a splitting depends on the flow patterns. Increasing the flow fluctuation frequency shortens this time span, which reaches a minimum before rising again due to inertia effects incorporated in the model. The size of the largest connected component after the splitting is rather independent of the flow fluctuation frequency but slightly decreases with the link capacities. Our findings carry important implications for real-world networks, such as electric power grids with a large share of renewable intermittent energy sources.
Lattice splitting under intermittent flows.
Schläpfer, Markus; Trantopoulos, Konstantinos
2010-05-01
We study the splitting of regular square lattices subject to stochastic intermittent flows. Various flow patterns are produced by different groupings of the nodes, based on their random alternation between two possible states. The resulting flows on the lattices decrease with the number of groups according to a power law. By Monte Carlo simulations we reveal how the time span until the occurrence of a splitting depends on the flow patterns. Increasing the flow fluctuation frequency shortens this time span, which reaches a minimum before rising again due to inertia effects incorporated in the model. The size of the largest connected component after the splitting is rather independent of the flow fluctuation frequency but slightly decreases with the link capacities. Our findings carry important implications for real-world networks, such as electric power grids with a large share of renewable intermittent energy sources. PMID:20866296
A transportable optical lattice clock
NASA Astrophysics Data System (ADS)
Vogt, Stefan; Häfner, Sebastian; Grotti, Jacopo; Koller, Silvio; Al-Masoudi, Ali; Sterr, Uwe; Lisdat, Christian
2016-06-01
We present the experimental setup and first results of PTB's transportable 87Sr clock. It consists of a physics package, several compact laser breadboards, and a transportable high finesse cavity for the clock laser. A comparison of the transportable system with our stationary optical lattice clock yields an instability of 2.2 x 10-15 √s/τ for the transportable clock. The current fractional uncertainty of 1 × 10-15 is still limited by the not yet fully evaluated light shift from the free running optical lattice laser operated near the magic wavelength. We are currently improving our transportable system to reach an uncertainty at or below the 10-17 level, which will finaly be limited by the uncertainty in blackbody radiation shift correction.
Nuclear Force from Lattice QCD
Ishii, N.; Aoki, S.; Hatsuda, T.
2007-07-13
The nucleon-nucleon (NN) potential is studied by lattice QCD simulations in the quenched approximation, using the plaquette gauge action and the Wilson quark action on a 32{sup 4} [{approx_equal}(4.4 fm){sup 4}] lattice. A NN potential V{sub NN}(r) is defined from the equal-time Bethe-Salpeter amplitude with a local interpolating operator for the nucleon. By studying the NN interaction in the {sup 1}S{sub 0} and {sup 3}S{sub 1} channels, we show that the central part of V{sub NN}(r) has a strong repulsive core of a few hundred MeV at short distances (r < or approx. 0.5 fm) surrounded by an attractive well at medium and long distances. These features are consistent with the known phenomenological features of the nuclear force.
Nuclear force from lattice QCD.
Ishii, N; Aoki, S; Hatsuda, T
2007-07-13
The nucleon-nucleon (NN) potential is studied by lattice QCD simulations in the quenched approximation, using the plaquette gauge action and the Wilson quark action on a 32(4) [approximately (4.4 fm)(4)] lattice. A NN potential V(NN)(r) is defined from the equal-time Bethe-Salpeter amplitude with a local interpolating operator for the nucleon. By studying the NN interaction in the (1)S(0) and (3)S(1) channels, we show that the central part of V(NN)(r) has a strong repulsive core of a few hundred MeV at short distances (r approximately < 0.5 fm) surrounded by an attractive well at medium and long distances. These features are consistent with the known phenomenological features of the nuclear force. PMID:17678213
Limiting vibration in space lattices
Midturi, S.
1997-12-01
Using finite-element analysis and other methods, engineers are evaluating ways to control the vibrations and extend the use of flexible, deployable structures in space. The exploration of the universe by the United States has led to many technological innovations for space travel. Among them are lightweight lattice structures and booms, which have been used on the Voyager probes to the outer planets, the Hubble space telescope,m and many other missions. Typical applications of lattice structures in space include instrument booms, antennae, and solar-array deployers and supports. Booms are designed for automatic deployment to a controlled length and retraction into a very compact stowage volume. Deployable solar booms are often subjected to severe vibration while in orbit, and vibration must be limited or completely eliminated for safe and satisfactory performance.
Innovations in Lattice QCD Algorithms
Konstantinos Orginos
2006-06-25
Lattice QCD calculations demand a substantial amount of computing power in order to achieve the high precision results needed to better understand the nature of strong interactions, assist experiment to discover new physics, and predict the behavior of a diverse set of physical systems ranging from the proton itself to astrophysical objects such as neutron stars. However, computer power alone is clearly not enough to tackle the calculations we need to be doing today. A steady stream of recent algorithmic developments has made an important impact on the kinds of calculations we can currently perform. In this talk I am reviewing these algorithms and their impact on the nature of lattice QCD calculations performed today.
Topological defects on the lattice
NASA Astrophysics Data System (ADS)
Aasen, David; Mong, Roger; Fendley, Paul
We construct defects in two-dimensional classical lattice models and one-dimensional quantum chains that are topologically invariant in the continuum limit. We show explicitly that these defect lines and their trivalent junctions commute with the transfer matrix/Hamiltonian. The resulting splitting and joining properties of the defect lines are exactly those of anyons in a topological phase. One useful consequence is an explicit definition of twisted boundary conditions that yield the precise shift in momentum quantization, and so provide a natural way of relating microscopic and macroscopic properties. Another is a generalization of Kramers-Wannier duality to a wide class of height models. Even more strikingly, we derive the modular transformation matrices explicitly and exactly from purely lattice considerations. We develop this construction for a variety of examples including the two-dimensional Ising model. Institute for Quantum Information and Matter, an NSF physics frontier center with support from the Moore Foundation. NSERC-PGSD.
Heterogeneous, weakly coupled map lattices
NASA Astrophysics Data System (ADS)
Sotelo Herrera, M.^{a.} Dolores; San Martín, Jesús; Porter, Mason A.
2016-07-01
Coupled map lattices (CMLs) are often used to study emergent phenomena in nature. It is typically assumed (unrealistically) that each component is described by the same map, and it is important to relax this assumption. In this paper, we characterize periodic orbits and the laminar regime of type-I intermittency in heterogeneous weakly coupled map lattices (HWCMLs). We show that the period of a cycle in an HWCML is preserved for arbitrarily small coupling strengths even when an associated uncoupled oscillator would experience a period-doubling cascade. Our results characterize periodic orbits both near and far from saddle-node bifurcations, and we thereby provide a key step for examining the bifurcation structure of heterogeneous CMLs.
Scattering in Quantum Lattice Gases
NASA Astrophysics Data System (ADS)
O'Hara, Andrew; Love, Peter
2009-03-01
Quantum Lattice Gas Automata (QLGA) are of interest for their use in simulating quantum mechanics on both classical and quantum computers. QLGAs are an extension of classical Lattice Gas Automata where the constraint of unitary evolution is added. In the late 1990s, David A. Meyer as well as Bruce Boghosian and Washington Taylor produced similar models of QLGAs. We start by presenting a unified version of these models and study them from the point of view of the physics of wave-packet scattering. We show that the Meyer and Boghosian-Taylor models are actually the same basic model with slightly different parameterizations and limits. We then implement these models computationally using the Python programming language and show that QLGAs are able to replicate the analytic results of quantum mechanics (for example reflected and transmitted amplitudes for step potentials and the Klein paradox).
Lattice Simulations and Infrared Conformality
Appelquist, Thomas; Fleming, George T.; Lin, Meifeng; Neil, Ethan T.; Schaich, David A
2011-09-01
We examine several recent lattice-simulation data sets, asking whether they are consistent with infrared conformality. We observe, in particular, that for an SU(3) gauge theory with 12 Dirac fermions in the fundamental representation, recent simulation data can be described assuming infrared conformality. Lattice simulations include a fermion mass m which is then extrapolated to zero, and we note that this data can be fit by a small-m expansion, allowing a controlled extrapolation. We also note that the conformal hypothesis does not work well for two theories that are known or expected to be confining and chirally broken, and that it does work well for another theory expected to be infrared conformal.
Apiary B Factory lattice design
Donald, M.H.R. ); Garren, A.A. )
1991-04-01
The Apiary B Factory is a proposed high-intensity electron-positron collider. This paper will present the lattice design for this facility, which envisions two rings with unequal energies in the PEP tunnel. The design has many interesting optical and geometrical features due to the needs to conform to the existing tunnel, and to achieve the necessary emittances, damping times and vacuum. Existing hardware is used to a maximum extent. 8 figs. 1 tab.
Apiary B Factory Lattice Design
Donald, M.H.R.; Garren, A.A.
1991-05-03
The Apiary B Factory is a proposed high-intensity electron-positron collider. This paper presents the lattice design for this facility, which envisions two rings with unequal energies in the PEP tunnel. The design has many interesting optical and geometrical features due to the needs to conform to the existing tunnel, and to achieve the necessary emittances, damping times and vacuum. Existing hardware is used to a maximum extent.
Scanning phononic lattices with ultrasound
Vines, R.E.; Wolfe, J.P.; Every, A.V.
1999-11-01
A method for probing the elastic properties of newly developed periodic structures using acoustic waves is introduced. Highly anisotropic transmission of surface acoustic waves is observed by continuously scanning the wave vector angle. Preliminary models of wave propagation through multilayers and two-dimensional lattices explain some of the experimental features, while other features can be attributed to the resonant excitation of interface waves. {copyright} {ital 1999} {ital The American Physical Society}
Fuzzy lattice neurocomputing (FLN) models.
Kaburlasos, V G; Petridis, V
2000-12-01
In this work it is shown how fuzzy lattice neurocomputing (FLN) emerges as a connectionist paradigm in the framework of fuzzy lattices (FL-framework) whose advantages include the capacity to deal rigorously with: disparate types of data such as numeric and linguistic data, intervals of values, 'missing' and 'don't care' data. A novel notation for the FL-framework is introduced here in order to simplify mathematical expressions without losing content. Two concrete FLN models are presented, namely 'sigma-FLN' for competitive clustering, and 'FLN with tightest fits (FLNtf)' for supervised clustering. Learning by the sigma-FLN, is rapid as it requires a single pass through the data, whereas learning by the FLNtf, is incremental, data order independent, polynomial theta(n3), and it guarantees maximization of the degree of inclusion of an input in a learned class as explained in the text. Convenient geometric interpretations are provided. The sigma-FLN is presented here as fuzzy-ART's extension in the FL-framework such that sigma-FLN widens fuzzy-ART's domain of application to (mathematical) lattices by augmenting the scope of both of fuzzy-ART's choice (Weber) and match functions, and by enhancing fuzzy-ART's complement coding technique. The FLNtf neural model is applied to four benchmark data sets of various sizes for pattern recognition and rule extraction. The benchmark data sets in question involve jointly numeric and nominal data with 'missing' and/or 'don't care' attribute values, whereas the lattices involved include the unit-hypercube, a probability space, and a Boolean algebra. The potential of the FL-framework in computing is also delineated. PMID:11156192
Mechanics of advanced fiber reinforced lattice composites
NASA Astrophysics Data System (ADS)
Fan, Hua-Lin; Zeng, Tao; Fang, Dai-Ning; Yang, Wei
2010-12-01
Fiber reinforced lattice composites are light-weight attractive due to their high specific strength and specific stiffness. In the past 10 years, researchers developed three-dimensional (3D) lattice trusses and two-dimensional (2D) lattice grids by various methods including interlacing, weaving, interlocking, filament winding and molding hot-press. The lattice composites have been applied in the fields of radar cross-section reduction, explosive absorption and heat-resistance. In this paper, topologies of the lattice composites, their manufacturing routes, as well as their mechanical and multifunctional applications, were surveyed.
Nuclear reactions from lattice QCD
Briceño, Raúl A.; Davoudi, Zohreh; Luu, Thomas C.
2015-01-13
In this study, one of the overarching goals of nuclear physics is to rigorously compute properties of hadronic systems directly from the fundamental theory of strong interactions, Quantum Chromodynamics (QCD). In particular, the hope is to perform reliable calculations of nuclear reactions which will impact our understanding of environments that occur during big bang nucleosynthesis, the evolution of stars and supernovae, and within nuclear reactors and high energy/density facilities. Such calculations, being truly ab initio, would include all two-nucleon and three- nucleon (and higher) interactions in a consistent manner. Currently, lattice QCD provides the only reliable option for performing calculations of some of the low-energy hadronic observables. With the aim of bridging the gap between lattice QCD and nuclear many-body physics, the Institute for Nuclear Theory held a workshop on Nuclear Reactions from Lattice QCD on March 2013. In this review article, we report on the topics discussed in this workshop and the path planned to move forward in the upcoming years.
Nuclear reactions from lattice QCD
Briceño, Raúl A.; Davoudi, Zohreh; Luu, Thomas C.
2015-01-13
In this study, one of the overarching goals of nuclear physics is to rigorously compute properties of hadronic systems directly from the fundamental theory of strong interactions, Quantum Chromodynamics (QCD). In particular, the hope is to perform reliable calculations of nuclear reactions which will impact our understanding of environments that occur during big bang nucleosynthesis, the evolution of stars and supernovae, and within nuclear reactors and high energy/density facilities. Such calculations, being truly ab initio, would include all two-nucleon and three- nucleon (and higher) interactions in a consistent manner. Currently, lattice QCD provides the only reliable option for performing calculationsmore » of some of the low-energy hadronic observables. With the aim of bridging the gap between lattice QCD and nuclear many-body physics, the Institute for Nuclear Theory held a workshop on Nuclear Reactions from Lattice QCD on March 2013. In this review article, we report on the topics discussed in this workshop and the path planned to move forward in the upcoming years.« less
Quantised vortices in polariton lattices
NASA Astrophysics Data System (ADS)
Berloff, Natalia
2015-11-01
The first comprehensive treatment of quantised vorticity in the light of research on vortices in modern fluid mechanics appeared in Russell Donnelly seminal research papers and summarized in his 1991 book ``Quantized Vortices in Helium II''. Recently quantized vortices have been studied in polariton condensates. Polaritons are the mixed light-matter quasi-particles that are formed in the strong exciton-photon coupling regime. Under non-resonant optical excitation rapid relaxation of carriers and bosonic stimulation result in the formation of a non-equilibrium polariton condensate characterized by a single many-body wave-function, therefore, naturally possessing quantized vortices. Polariton condensates can be imprinted into any two-dimensional lattice by spatial modulation of the pumping laser and form vortices via interacting outfows from the pumping sites. Optically pumped polariton condensates can be injected in lattice configurations with arbitrary density profiles offering the possibility to control the kinetics of the condensate and therefore the number and location of vortices. I will present some new developments in theoretical and experimental studies of quantized vortices in polariton condensates and discuss possible practical implementations of polariton lattices.
Ectopic A-lattice seams destabilize microtubules
Katsuki, Miho; Drummond, Douglas R.; Cross, Robert A.
2014-01-01
Natural microtubules typically include one A-lattice seam within an otherwise helically symmetric B-lattice tube. It is currently unclear how A-lattice seams influence microtubule dynamic instability. Here we find that including extra A-lattice seams in GMPCPP microtubules, structural analogues of the GTP caps of dynamic microtubules, destabilizes them, enhancing their median shrinkage rate by >20-fold. Dynamic microtubules nucleated by seeds containing extra A-lattice seams have growth rates similar to microtubules nucleated by B-lattice seeds, yet have increased catastrophe frequencies at both ends. Furthermore, binding B-lattice GDP microtubules to a rigor kinesin surface stabilizes them against shrinkage, whereas microtubules with extra A-lattice seams are stabilized only slightly. Our data suggest that introducing extra A-lattice seams into dynamic microtubules destabilizes them by destabilizing their GTP caps. On this basis, we propose that the single A-lattice seam of natural B-lattice MTs may act as a trigger point, and potentially a regulation point, for catastrophe. PMID:24463734
Lattice Green's functions in all dimensions
NASA Astrophysics Data System (ADS)
Guttmann, Anthony J.
2010-07-01
We give a systematic treatment of lattice Green's functions (LGF) on the d-dimensional diamond, simple cubic, body-centred cubic and face-centred cubic lattices for arbitrary dimensionality d >= 2 for the first three lattices, and for 2 <= d <= 5 for the hyper-fcc lattice. We show that there is a close connection between the LGF of the d-dimensional hyper-cubic lattice and that of the (d - 1)-dimensional diamond lattice. We give constant-term formulations of LGFs for each of these lattices in all dimensions. Through a still under-developed connection with Mahler measures, we point out an unexpected connection between the coefficients of the sc, bcc and diamond LGFs and some Ramanujan-type formulae for 1/π.
Lattice Truss Structural Response Using Energy Methods
NASA Technical Reports Server (NTRS)
Kenner, Winfred Scottson
1996-01-01
A deterministic methodology is presented for developing closed-form deflection equations for two-dimensional and three-dimensional lattice structures. Four types of lattice structures are studied: beams, plates, shells and soft lattices. Castigliano's second theorem, which entails the total strain energy of a structure, is utilized to generate highly accurate results. Derived deflection equations provide new insight into the bending and shear behavior of the four types of lattices, in contrast to classic solutions of similar structures. Lattice derivations utilizing kinetic energy are also presented, and used to examine the free vibration response of simple lattice structures. Derivations utilizing finite element theory for unique lattice behavior are also presented and validated using the finite element analysis code EAL.
... AT III) is a protein that helps control blood clotting. A blood test can determine the amount of ... may mean you have an increased risk of blood clotting. This can occur when there is not enough ...
... be due to: Bone marrow transplant Disseminated intravascular coagulation (DIC) AT III deficiency, an inherited condition Liver ... Schmaier AH, Miller JL. Coagulation and fibrinolysis. In: McPherson ... Management by Laboratory Methods . 22nd ed. Philadelphia, PA: ...
Random-field Ising model on isometric lattices: Ground states and non-Porod scattering
NASA Astrophysics Data System (ADS)
Bupathy, Arunkumar; Banerjee, Varsha; Puri, Sanjay
2016-01-01
We use a computationally efficient graph cut method to obtain ground state morphologies of the random-field Ising model (RFIM) on (i) simple cubic (SC), (ii) body-centered cubic (BCC), and (iii) face-centered cubic (FCC) lattices. We determine the critical disorder strength Δc at zero temperature with high accuracy. For the SC lattice, our estimate (Δc=2.278 ±0.002 ) is consistent with earlier reports. For the BCC and FCC lattices, Δc=3.316 ±0.002 and 5.160 ±0.002 , respectively, which are the most accurate estimates in the literature to date. The small-r behavior of the correlation function exhibits a cusp regime characterized by a cusp exponent α signifying fractal interfaces. In the paramagnetic phase, α =0.5 ±0.01 for all three lattices. In the ferromagnetic phase, the cusp exponent shows small variations due to the lattice structure. Consequently, the interfacial energy Ei(L ) for an interface of size L is significantly different for the three lattices. This has important implications for nonequilibrium properties.
Unbiased sampling of lattice Hamilton path ensembles
NASA Astrophysics Data System (ADS)
Mansfield, Marc L.
2006-10-01
Hamilton paths, or Hamiltonian paths, are walks on a lattice which visit each site exactly once. They have been proposed as models of globular proteins and of compact polymers. A previously published algorithm [Mansfield, Macromolecules 27, 5924 (1994)] for sampling Hamilton paths on simple square and simple cubic lattices is tested for bias and for efficiency. Because the algorithm is a Metropolis Monte Carlo technique obviously satisfying detailed balance, we need only demonstrate ergodicity to ensure unbiased sampling. Two different tests for ergodicity (exact enumeration on small lattices, nonexhaustive enumeration on larger lattices) demonstrate ergodicity unequivocally for small lattices and provide strong support for ergodicity on larger lattices. Two other sampling algorithms [Ramakrishnan et al., J. Chem. Phys. 103, 7592 (1995); Lua et al., Polymer 45, 717 (2004)] are both known to produce biases on both 2×2×2 and 3×3×3 lattices, but it is shown here that the current algorithm gives unbiased sampling on these same lattices. Successive Hamilton paths are strongly correlated, so that many iterations are required between statistically independent samples. Rules for estimating the number of iterations needed to dissipate these correlations are given. However, the iteration time is so fast that the efficiency is still very good except on extremely large lattices. For example, even on lattices of total size 10×10×10 we are able to generate tens of thousands of uncorrelated Hamilton paths per hour of CPU time.
Colliding-beam-accelerator lattice
Claus, J.; Cornacchia, M.; Courant, E.D.; Parzen, G.
1983-01-01
We describe the lattice of the Colliding Beam Accelerator, a 400 x 400 GeV pp facility proposed for construction at Brookhaven National Laboratory. The structure adopted is very versatile, in part in consequence of its desirable behavior as function of momentum deviation and as function of the betatron tunes. Each of the six insertions can be arranged to meet specific requirements at the crossing points as illustrated by a discussion of the tuneable low-beta insertions. The luminosity in these low-beta insertions (2 x 10/sup 33/ cm/sup -2/ sec/sup -1/) would be an order of magnitude larger than the standard insertions.
Solitary waves on tensegrity lattices
NASA Astrophysics Data System (ADS)
Fraternali, F.; Senatore, L.; Daraio, C.
2012-06-01
We study the dynamics of lattices formed by masses connected through tensegrity prisms. By employing analytic and numerical arguments, we show that such structures support two limit dynamic regimes controlled by the prisms' properties: (i) in the low-energy (sonic) regime the system supports the formation and propagation of solitary waves which exhibit sech2 shape and (ii) in the high-energy (ultrasonic) regime the system supports atomic-scale localization. Such peculiar features found in periodic arrays of tensegrity structures suggest their use for the creation of new composite materials (here called "tensegrity materials") of potential interest for applications in impact absorption, energy localization and in new acoustic devices.
Lattice models of biological growth
Young, D.A.; Corey, E.M. )
1990-06-15
We show that very simple iterative rules for the growth of cells on a two-dimensional lattice can simulate biological-growth phenomena realistically. We discuss random cellular automata models for the growth of fern gametophytes, branching fungi, and leaves, and for shape transformations useful in the study of biological variation and evolution. Although there are interesting analogies between biological and physical growth processes, we stress the uniqueness of biological automata behavior. The computer growth algorithms that successfully mimic observed growth behavior may be helpful in determining the underlying biochemical mechanisms of growth regulation.
Multi-stable cylindrical lattices
NASA Astrophysics Data System (ADS)
Pirrera, Alberto; Lachenal, Xavier; Daynes, Stephen; Weaver, Paul M.; Chenchiah, Isaac V.
2013-11-01
We present a cylindrical lattice structure that mimics the behaviour of the virus bacteriophage T4 in having two (or more) stable states which differ in their radii and length. While the virus achieves bistability through molecular mechanisms we use composite materials to exploit the interplay between pre-stress, material properties and structural geometry. We demonstrate (computationally) that multi-stability is a robust phenomenon. We also show (analytically) that it is possible to choose the design variables so that the energy is independent of the radius, thus resulting in every state of the structure being stable.
Dipolar molecules in optical lattices.
Sowiński, Tomasz; Dutta, Omjyoti; Hauke, Philipp; Tagliacozzo, Luca; Lewenstein, Maciej
2012-03-16
We study the extended Bose-Hubbard model describing an ultracold gas of dipolar molecules in an optical lattice, taking into account all on-site and nearest-neighbor interactions, including occupation-dependent tunneling and pair tunneling terms. Using exact diagonalization and the multiscale entanglement renormalization ansatz, we show that these terms can destroy insulating phases and lead to novel quantum phases. These considerable changes of the phase diagram have to be taken into account in upcoming experiments with dipolar molecules. PMID:22540482
Detecting monopoles on the lattice
Bonati, Claudio; Di Giacomo, Adriano; D'Elia, Massimo
2010-11-01
We address the issue why the number and the location of magnetic monopoles detected on lattice configurations are gauge dependent, in contrast with the physical expectation that monopoles have a gauge-invariant status. By use of the non-Abelian Bianchi identities we show that monopoles are gauge-invariant, but the efficiency of the technique usually adopted to detect them depends on the choice of the gauge in a well understood way. In particular we have studied a class of gauges which interpolate between the Maximal Abelian gauge, where all monopoles are observed, and the Landau gauge, where all monopoles escape detection.
GLAD: A Generic LAttice Debugger
Lee, M.J.
1991-11-01
Today, numerous simulation and analysis codes exist for the design, commission, and operation of accelerator beam lines. There is a need to develop a common user interface and database link to run these codes interactively. This paper will describe a proposed system, GLAD (Generic LAttice Debugger), to fulfill this need. Specifically, GLAD can be used to find errors in beam lines during commissioning, control beam parameters during operation, and design beam line optics and error correction systems for the next generation of linear accelerators and storage rings.
An Isochronous Lattice for PEP
Corbett, W.J.; Donald, M.H.R.; Garren, A.A.
1991-04-01
With e{sup +}e{sup -} storage rings operating in a quasi-isochronous mode, it might be possible to produce short bunches with length {sigma}{sub z} < 1 cm. The unique characteristics of the short bunches could then be utilized for synchrotron radiation applications or colliders with mm-scale {beta}*. In principle, the design of a quasi-isochronous storage ring is relatively straight-forward, but experimental studies with electron storage rings in this configuration have not been carried out. The purpose of this paper is to demonstrate that an isochronous lattice design is compatible with PEP given a minimum of hardware modifications.
Lattice Boltzmann methods in Geosciences
NASA Astrophysics Data System (ADS)
Huber, Christian; Parmigiani, Andrea; Su, Yanqing
2014-05-01
Numerical models often offer the only possible approach to study the complex non-linear dynamics of geodynamical processes that are difficult or impossible to scale for laboratory experiments. The development of improved computer resources has allowed the emergence of large-scale parallel computations in Earth Sciences. These resources have lead to an increasing complexity in models where a greater number of adjustable parameters arise. Although the increasing number of free parameters offers a greater flexibility to fit satisfyingly the set of available constraints (e.g. geochemical, structural) it also provides new challenges in terms of the size of the parameter space and non-uniqueness of model solutions. Another significant challenge associated with state-of-the-art models is that their complexity is in general associated with the addition of parameterizations of the unresolved (small) scale processes. This trend calls for the development of complementary high-performance models to constrain the physics at small-scales where mass, momentum and energy exchanges at interfaces between different phases control the dynamics in heterogeneous media. We argue that more attention should be devoted to the development of multiphase numerical modeling at the granular (pore) scale to investigate the dynamical behavior of heterogeneous media and the emergence of feedbacks that influence the response of these media at much greater scales. The lattice Boltzmann method is a paradigm that emerged almost three decades ago. It is based on kinetic theory and follows a bottom-up approach that contrast the top-down strategy of standard methods such as Finite Volumes, FEM and Finite Differences. Lattice Boltzmann is ideally suited to handle the complex dynamics of multiphase systems at small spatial scales and is very efficient for parallel programing. In this presentation, we discuss the development of different lattice Boltzmann models developed in our group over the last years
Fractal lattice of gelatin nanoglobules
NASA Astrophysics Data System (ADS)
Novikov, D. V.; Krasovskii, A. N.
2012-11-01
The globular structure of polymer coatings on a glass, which were obtained from micellar solutions of gelatin in the isooctane-water-sodium (bis-2-ethylhexyl) sulfosuccinate system, has been studied using electron microscopy. It has been shown that an increase in the average globule size is accompanied by the formation of a fractal lattice of nanoglobules and a periodic physical network of macromolecules in the coating. The stability of such system of the "liquid-in-a-solid" type is limited by the destruction of globules and the formation of a homogeneous network structure of the coating.
Localization of Waves in Merged Lattices.
Alagappan, G; Png, C E
2016-01-01
This article describes a new two-dimensional physical topology-merged lattice, that allows dense number of wave localization states. Merged lattices are obtained as a result of merging two lattices of scatters of the same space group, but with slightly different spatial resonances. Such merging creates two-dimensional scattering "beats" which are perfectly periodic on the longer spatial scale. On the shorter spatial scale, the systematic breakage of the translational symmetry leads to strong wave scattering, and this causes the occurrences of wave localization states. Merged Lattices promises variety of localization states including tightly confined, and ring type annular modes. The longer scale perfect periodicity of the merged lattice, enables complete prediction and full control over the density of the localization states and its' quality factors. In addition, the longer scale periodicity, also allows design of integrated slow wave components. Merged lattices, thus, can be engineered easily to create technologically beneficial applications. PMID:27535096
Working Group Report: Lattice Field Theory
Blum, T.; et al.,
2013-10-22
This is the report of the Computing Frontier working group on Lattice Field Theory prepared for the proceedings of the 2013 Community Summer Study ("Snowmass"). We present the future computing needs and plans of the U.S. lattice gauge theory community and argue that continued support of the U.S. (and worldwide) lattice-QCD effort is essential to fully capitalize on the enormous investment in the high-energy physics experimental program. We first summarize the dramatic progress of numerical lattice-QCD simulations in the past decade, with some emphasis on calculations carried out under the auspices of the U.S. Lattice-QCD Collaboration, and describe a broad program of lattice-QCD calculations that will be relevant for future experiments at the intensity and energy frontiers. We then present details of the computational hardware and software resources needed to undertake these calculations.
Localization of Waves in Merged Lattices
Alagappan, G.; Png, C. E.
2016-01-01
This article describes a new two–dimensional physical topology–merged lattice, that allows dense number of wave localization states. Merged lattices are obtained as a result of merging two lattices of scatters of the same space group, but with slightly different spatial resonances. Such merging creates two–dimensional scattering “beats” which are perfectly periodic on the longer spatial scale. On the shorter spatial scale, the systematic breakage of the translational symmetry leads to strong wave scattering, and this causes the occurrences of wave localization states. Merged Lattices promises variety of localization states including tightly confined, and ring type annular modes. The longer scale perfect periodicity of the merged lattice, enables complete prediction and full control over the density of the localization states and its’ quality factors. In addition, the longer scale periodicity, also allows design of integrated slow wave components. Merged lattices, thus, can be engineered easily to create technologically beneficial applications. PMID:27535096
Relationship between lattice disorder and non-Fermi liquid properties in annealed UCu_4Pd
NASA Astrophysics Data System (ADS)
Booth, C. H.; Scheidt, E.-W.; Weber, A.; Maurer, D.; Kehrein, S.
2002-03-01
The heat capacity, electrical resistivity and lattice parameter of the lattice-disordered, non-Fermi liquid (NFL) material UCu_4Pd have been shown to be sensitive to annealing time.(A. Weber et al.), Phys. Rev. B 63, 205116 (2001). We present x-ray absorption fine-structure (XAFS) measurements from the Pd K and U L_III edges that show the percentage of Pd atoms on nominally Cu 16e sites within the C15b crystal structure decreases from about 27% to 19% upon the first day of annealing, and does not change measurably with further annealing. Moreover, the U-Cu bond length distribution width, σ, narrows monotonically, with Δ σ^2 = -0.00035(3) Åafter 14 days of annealing. These changes in the local lattice properties will be related to the measured changes in the NFL properties.
Coincident site lattice-matched growth of semiconductors on substrates using compliant buffer layers
Norman, Andrew
2016-08-23
A method of producing semiconductor materials and devices that incorporate the semiconductor materials are provided. In particular, a method is provided of producing a semiconductor material, such as a III-V semiconductor, on a silicon substrate using a compliant buffer layer, and devices such as photovoltaic cells that incorporate the semiconductor materials. The compliant buffer material and semiconductor materials may be deposited using coincident site lattice-matching epitaxy, resulting in a close degree of lattice matching between the substrate material and deposited material for a wide variety of material compositions. The coincident site lattice matching epitaxial process, as well as the use of a ductile buffer material, reduce the internal stresses and associated crystal defects within the deposited semiconductor materials fabricated using the disclosed method. As a result, the semiconductor devices provided herein possess enhanced performance characteristics due to a relatively low density of crystal defects.
Observing dynamical SUSY breaking with lattice simulation
Kanamori, Issaku
2008-11-23
On the basis of the recently developed lattice formulation of supersymmetric theories which keeps a part of the supersymmetry, we propose a method of observing dynamical SUSY breaking with lattice simulation. We use Hamiltonian as an order parameter and measure the ground state energy as a zero temperature limit of the finite temperature simulation. Our method provides a way of obtaining a physical result from the lattice simulation for supersymmetric theories.
Trapping Rydberg Atoms in an Optical Lattice
NASA Astrophysics Data System (ADS)
Anderson, Sarah E.
2012-06-01
Optical lattice traps for Rydberg atoms are of interest in advanced science and in practical applications. After a brief discussion of these areas of interest, I will review some basics of optical Rydberg-atom trapping. The trapping potential experienced by a Rydberg atom in an optical lattice is given by the spatial average of the free-electron ponderomotive energy weighted by the Rydberg electron's probability distribution. I will then present experimental results on the trapping of ^85Rb Rydberg atoms in a one-dimensional ponderomotive optical lattice (wavelength 1064 nm). The principal methods employed to study the lattice performance are microwave spectroscopy, which is used to measure the lattice's trapping efficiency, and photo-ionization, which is used to measure the dwell time of the atoms in the lattice. I have achieved a 90% trapping efficiency for ^85Rb 50S atoms by inverting the lattice immediately after laser excitation of ground-state atoms into Rydberg states. I have characterized the dwell time of the atoms in the lattice using photo-ionization of 50D5/2 atoms. In continued work, I have explored the dependence of the Rydberg-atom trapping potential on the angular portion of the atomic wavefunction. Distinct angular states exhibit different trapping behavior in the optical lattice, depending on how their wavefunctions are oriented relative to the lattice planes. Specifically, I have measured the lattice potential depth of sublevels of ^85Rb nD atoms (50<=n<=65) in a one-dimensional optical lattice with a transverse DC electric field. The trapping behavior varies substantially for the various angular sublevels, in agreement with theory. The talk will conclude with an outlook into planned experiments.
Experimental generation of optical coherence lattices
NASA Astrophysics Data System (ADS)
Chen, Yahong; Ponomarenko, Sergey A.; Cai, Yangjian
2016-08-01
We report experimental generation and measurement of recently introduced optical coherence lattices. The presented optical coherence lattice realization technique hinges on a superposition of mutually uncorrelated partially coherent Schell-model beams with tailored coherence properties. We show theoretically that information can be encoded into and, in principle, recovered from the lattice degree of coherence. Our results can find applications to image transmission and optical encryption.
Computational study of lattice models
NASA Astrophysics Data System (ADS)
Zujev, Aleksander
This dissertation is composed of the descriptions of a few projects undertook to complete my doctorate at the University of California, Davis. Different as they are, the common feature of them is that they all deal with simulations of lattice models, and physics which results from interparticle interactions. As an example, both the Feynman-Kikuchi model (Chapter 3) and Bose-Fermi mixture (Chapter 4) deal with the conditions under which superfluid transitions occur. The dissertation is divided into two parts. Part I (Chapters 1-2) is theoretical. It describes the systems we study - superfluidity and particularly superfluid helium, and optical lattices. The numerical methods of working with them are described. The use of Monte Carlo methods is another unifying theme of the different projects in this thesis. Part II (Chapters 3-6) deals with applications. It consists of 4 chapters describing different projects. Two of them, Feynman-Kikuchi model, and Bose-Fermi mixture are finished and published. The work done on t - J model, described in Chapter 5, is more preliminary, and the project is far from complete. A preliminary report on it was given on 2009 APS March meeting. The Isentropic project, described in the last chapter, is finished. A report on it was given on 2010 APS March meeting, and a paper is in preparation. The quantum simulation program used for Bose-Fermi mixture project was written by our collaborators Valery Rousseau and Peter Denteneer. I had written my own code for the other projects.
Biagini, M.E.; Raimondi, P.; Piminov, P.; Sinyatkin, S.; Nosochkov, Y.; Wittmer, W.; /SLAC
2010-08-25
The SuperB asymmetric e{sup +}e{sup -} collider is designed for 10{sup 36} cm{sup -2} s{sup -1} luminosity and beam energies of 6.7 and 4.18 GeV for e{sup +} and e{sup -} respectively. The High and Low Energy Rings (HER and LER) have one Interaction Point (IP) with 66 mrad crossing angle. The 1258 m rings fit to the INFN-LNF site at Frascati. The ring emittance is minimized for the high luminosity. The Final Focus (FF) chromaticity correction is optimized for maximum transverse acceptance and energy bandwidth. Included Crab Waist sextupoles suppress betatron resonances induced in the collisions with a large Piwinski angle. The LER Spin Rotator sections provide longitudinally polarized electron beam at the IP. The lattice is flexible for tuning the machine parameters and compatible with reusing the PEP-II magnets, RF cavities and other components. Details of the lattice design are presented.
The Fermilab lattice information repository
Ostiguy, J.-F.; Michelotti, L.; McCusker-Whiting, M.; Kriss, M.; /Fermilab
2005-05-01
Over the years, it has become increasingly obvious that a centralized lattice and machine information repository with the capability of keeping track of revision information could be of great value. This is especially true in the context of a large accelerator laboratory like Fermilab with six rings and sixteen beamlines operating in various modes and configurations, constantly subject to modifications, improvements and even major redesign. While there exist a handful of potentially suitable revision systems--both freely available and commercial--our experience has shown that expecting beam physicists to become fully conversant with complex revision system software used on an occasional basis is neither realistic nor practical. In this paper, we discuss technical aspects of the FNAL lattice repository, whose fully web-based interface hides the complexity of Subversion, a comprehensive open source revision system. The FNAL repository has been operational since September 2004; the unique architecture of ''Subversion'' has been a key ingredient of the technical success of its implementation.
Collapsing lattice animals and lattice trees in two dimensions
NASA Astrophysics Data System (ADS)
Hsu, Hsiao-Ping; Grassberger, Peter
2005-06-01
We present high statistics simulations of weighted lattice bond animals and lattice trees on the square lattice, with fugacities for each non-bonded contact and for each bond between two neighbouring monomers. The simulations are performed using a newly developed sequential sampling method with resampling, very similar to the pruned-enriched Rosenbluth method (PERM) used for linear chain polymers. We determine with high precision the line of second-order transitions from an extended to a collapsed phase in the resulting two-dimensional phase diagram. This line includes critical bond percolation as a multicritical point, and we verify that this point divides the line into different universality classes. One of them corresponds to the collapse driven by contacts and includes the collapse of (weakly embeddable) trees. There is some evidence that the other is subdivided again into two parts with different universality classes. One of these (at the far side from collapsing trees) is bond driven and is represented by the Derrida-Herrmann model of animals having bonds only (no contacts). Between the critical percolation point and this bond-driven collapse seems to be an intermediate regime, whose other end point is a multicritical point P* where a transition line between two collapsed phases (one bond driven and the other contact driven) sparks off. This point P* seems to be attractive (in the renormalization group sense) from the side of the intermediate regime, so there are four universality classes on the transition line (collapsing trees, critical percolation, intermediate regime, and Derrida-Herrmann). We obtain very precise estimates for all critical exponents for collapsing trees. It is already harder to estimate the critical exponents for the intermediate regime. Finally, it is very difficult to obtain with our method good estimates of the critical parameters of the Derrida-Herrmann universality class. As regards the bond-driven to contact-driven transition in the
Subwavelength Lattice Optics by Evolutionary Design
2015-01-01
This paper describes a new class of structured optical materials—lattice opto-materials—that can manipulate the flow of visible light into a wide range of three-dimensional profiles using evolutionary design principles. Lattice opto-materials are based on the discretization of a surface into a two-dimensional (2D) subwavelength lattice whose individual lattice sites can be controlled to achieve a programmed optical response. To access a desired optical property, we designed a lattice evolutionary algorithm that includes and optimizes contributions from every element in the lattice. Lattice opto-materials can exhibit simple properties, such as on- and off-axis focusing, and can also concentrate light into multiple, discrete spots. We expanded the unit cell shapes of the lattice to achieve distinct, polarization-dependent optical responses from the same 2D patterned substrate. Finally, these lattice opto-materials can also be combined into architectures that resemble a new type of compound flat lens. PMID:25380062
Fractionalized topological defects in optical lattices
NASA Astrophysics Data System (ADS)
Zhang, Xing-Hai; Fan, Wen-Jun; Shi, Jin-Wei; Kou, Su-Peng
2015-10-01
Topological objects are interesting topics in various fields of physics ranging from condensed matter physics to the grand unified and superstring theories. Among those, ultracold atoms provide a playground to study the complex topological objects. In this paper we present a proposal to realize an optical lattice with stable fractionalized topological objects. In particular, we generate the fractionalized topological fluxes and fractionalized skyrmions on two-dimensional optical lattices and fractionalized monopoles on three-dimensional optical lattices. These results offer a new approach to study the quantum many-body systems on optical lattices of ultracold quantum gases with controllable topological defects, including dislocations, topological fluxes and monopoles.
Transmission Electron Microscope Measures Lattice Parameters
NASA Technical Reports Server (NTRS)
Pike, William T.
1996-01-01
Convergent-beam microdiffraction (CBM) in thermionic-emission transmission electron microscope (TEM) is technique for measuring lattice parameters of nanometer-sized specimens of crystalline materials. Lattice parameters determined by use of CBM accurate to within few parts in thousand. Technique developed especially for use in quantifying lattice parameters, and thus strains, in epitaxial mismatched-crystal-lattice multilayer structures in multiple-quantum-well and other advanced semiconductor electronic devices. Ability to determine strains in indivdual layers contributes to understanding of novel electronic behaviors of devices.
Bosonic edge states in gapped honeycomb lattices
NASA Astrophysics Data System (ADS)
Guo, Huaiming; Niu, Yuekun; Chen, Shu; Feng, Shiping
2016-03-01
By quantum Monte Carlo simulations of bosons in gapped honeycomb lattices, we show the existence of bosonic edge states. For a single layer honeycomb lattice, bosonic edge states can be controlled to appear, cross the gap, and merge into bulk states by an on-site potential applied on the outermost sites of the boundary. On a bilayer honeycomb lattice, A bosonic edge state traversing the gap at half filling is demonstrated. The topological origin of the bosonic edge states is discussed with pseudo Berry curvature. The results will simulate experimental studies of these exotic bosonic edge states with ultracold bosons trapped in honeycomb optical lattices.
Vortex lattice of surface plasmon polaritons
NASA Astrophysics Data System (ADS)
Dzedolik, Igor V.; Lapayeva, Svetlana; Pereskokov, Vladislav
2016-07-01
We theoretically investigate the formation of a plasmon polariton vortex lattice on a metal surface following the interference of surface plasmon polaritons (SPPs). The plasmon polariton vortex lattice is formed by the interference of the SPP transverse-magnetic mode (TM-mode) and electric mode (E-mode) in the presence of the inhomogeneity with a curvilinear boundary on the surface of the metal layer. The SPP vortex lattice can be controlled by changing the configuration of the boundary. Weak nonlinearity of the metal permittivity does not change the interference pattern, but it increases the propagation length of the SPPs and, therefore, the area of the vortex lattice too.
Modeling dynamical geometry with lattice gas automata
Hasslacher, B.; Meyer, D.A.
1998-06-27
Conventional lattice gas automata consist of particles moving discretely on a fixed lattice. While such models have been quite successful for a variety of fluid flow problems, there are other systems, e.g., flow in a flexible membrane or chemical self-assembly, in which the geometry is dynamical and coupled to the particle flow. Systems of this type seem to call for lattice gas models with dynamical geometry. The authors construct such a model on one dimensional (periodic) lattices and describe some simulations illustrating its nonequilibrium dynamics.
Subwavelength lattice optics by evolutionary design.
Huntington, Mark D; Lauhon, Lincoln J; Odom, Teri W
2014-12-10
This paper describes a new class of structured optical materials--lattice opto-materials--that can manipulate the flow of visible light into a wide range of three-dimensional profiles using evolutionary design principles. Lattice opto-materials are based on the discretization of a surface into a two-dimensional (2D) subwavelength lattice whose individual lattice sites can be controlled to achieve a programmed optical response. To access a desired optical property, we designed a lattice evolutionary algorithm that includes and optimizes contributions from every element in the lattice. Lattice opto-materials can exhibit simple properties, such as on- and off-axis focusing, and can also concentrate light into multiple, discrete spots. We expanded the unit cell shapes of the lattice to achieve distinct, polarization-dependent optical responses from the same 2D patterned substrate. Finally, these lattice opto-materials can also be combined into architectures that resemble a new type of compound flat lens. PMID:25380062
Trace maps of general Padovan lattices
NASA Astrophysics Data System (ADS)
Tong, Peiqing
2000-07-01
The two kinds of seven-dimensional trace maps of a new class of three-component quasiperiodic lattices, which are constructed based on the general Padovan sequences Sl+1 ={ Sl-1 m, Sl-2 n}, are derived for arbitrary integer value of m and n. It is shown that these lattices can be grouped into two distinct class. The lattices in class I correspond to n=1 and arbitrary m. They are shown to have volume-preserving second kind maps. The results are compared with those of other three-component quasiperiodic lattices.
Elastic lattice in an incommensurate background
Dickman, R.; Chudnovsky, E.M. )
1995-01-01
We study a harmonic triangular lattice, which relaxes in the presence of an incommensurate short-wavelength potential. Monte Carlo simulations reveal that the elastic lattice exhibits only short-ranged translational correlations, despite the absence of defects in either lattice. Extended orientational order, however, persists in the presence of the background. Translational correlation lengths exhibit approximate power-law dependence upon cooling rate and background strength. Our results may be relevant to Wigner crystals, atomic monolayers on crystals surfaces, and flux-line and magnetic bubble lattices.
GaNPAs Solar Cells Lattice-Matched To GaP: Preprint
Geisz, J. F.; Friedman, D. J.; Kurtz, S.
2002-05-01
This conference paper describes the III-V semiconductors grown on silicon substrates are very attractive for lower-cost, high-efficiency multijunction solar cells, but lattice-mismatched alloys that result in high dislocation densities have been unable to achieve satisfactory performance. GaNxP1-x-yAsy is a direct-gap III-V alloy that can be grown lattice-matched to Si when y= 4.7x - 0.1. We propose the use of lattice-matched GaNPAs on silicon for high-efficiency multijunction solar cells. We have grown GaNxP1-x-yAsy on GaP (with a similar lattice constant to silicon) by metal-organic chemical vapor phase epitaxy with direct band-gaps in the range of 1.5 to 2.0 eV. We demonstrate the performance of single-junction GaNxP1-x-yAsy solar cells grown on GaP substrates and discuss the prospects for the development of monolithic high-efficiency multijunction solar cells based on silicon substrates.
GaNPAs Solar Cells that Can Be Lattice-Matched to Silicon
Geisz, J. F.; Friedman, D. J.; McMahon, W. E.; Ptak, A. J.; Kibbler, A. E.; Olson, J. M.; Kurtz, S.; Kramer, C.; Young, M.; Duda, A.; Reedy, R. C.; Keyes, B. M.; Dippo, P.; Metzger, W. K.
2003-05-01
III-V semiconductors grown on silicon substrates are very attractive for lower-cost, high-efficiency multijunction solar cells, but lattice-mismatched alloys that result in high dislocation densities have been unable to achieve satisfactory performance. GaNxP1-x-yAsy is a direct-gap III-V alloy that can be grown lattice-matched to Si when y= 4.7x - 0.1. We have proposed the use of lattice-matched GaNPAs on silicon for high-efficiency multijunction solar cells. We have grown GaNxP1-x-yAsy on GaP (with a similar lattice constant to silicon) by metal-organic chemical vapor phase epitaxy with direct bandgaps in the range of 1.5 to 2.0 eV. We have demonstrated the performance of single-junction GaNxP1-x-yAsy solar cells grown on GaP substrates and shown improvements in material quality by reducing carbon and hydrogen impurities through optimization of growth conditions. We have achieved quantum efficiencies (QE) in these cells as high as 60% and PL lifetimes as high as 3.0 ns.
Fusion Power Demonstration III
Lee, J.D.
1985-07-01
This is the third in the series of reports covering the Fusion Power Demonstration (FPD) design study. This volume considers the FPD-III configuration that incorporates an octopole end plug. As compared with the quadrupole end-plugged designs of FPD-I and FPD-II, this octopole configuration reduces the number of end cell magnets and shortens the minimum ignition length of the central cell. The end-cell plasma length is also reduced, which in turn reduces the size and cost of the end cell magnets and shielding. As a contiuation in the series of documents covering the FPD, this report does not stand alone as a design description of FPD-III. Design details of FPD-III subsystems that do not differ significantly from those of the FPD-II configuration are not duplicated in this report.
NASA Technical Reports Server (NTRS)
1961-01-01
Looking more like surgeons, these technicians wearing 'cleanroom' attire inspect the Pioneer III probe before shipping it to Cape Canaveral, Florida. Pioneer III was launched on December 6, 1958 aboard a Juno II rocket at the Atlantic Missile Range, Cape Canaveral, Florida. The mission objectives were to measure the radiation intensity of the Van Allen radiation belt, test long range communication systems, the launch vehicle and other subsystems. The Juno II failed to reach proper orbital escape velocity. The probe re-entered the Earth's atmosphere on December 7th ending its brief mission.
Cold atoms in a rotating optical lattice
NASA Astrophysics Data System (ADS)
Foot, Christopher J.
2009-05-01
We have demonstrated a novel experimental arrangement which can rotate a two-dimensional optical lattice at frequencies up to several kilohertz. Our arrangement also allows the periodicity of the optical lattice to be varied dynamically, producing a 2D ``accordion lattice'' [1]. The angles of the laser beams are controlled by acousto-optic deflectors and this allows smooth changes with little heating of the trapped cold (rubidium) atoms. We have loaded a BEC into lattices with periodicities ranging from 1.8μm to 18μm, observing the collapse and revival of the diffraction orders of the condensate over a large range of lattice parameters as recently reported by a group in NIST [2]. We have also imaged atoms in situ in a 2D lattice over a range of lattice periodicities. Ultracold atoms in a rotating lattice can be used for the direct quantum simulation of strongly correlated systems under large effective magnetic fields, i.e. the Hamiltonian of the atoms in the rotating frame resembles that of a charged particle in a strong magnetic field. In the future, we plan to use this to investigate a range of phenomena such as the analogue of the fractional quantum Hall effect. [4pt] [1] R. A. Williams, J. D. Pillet, S. Al-Assam, B. Fletcher, M. Shotter, and C. J. Foot, ``Dynamic optical lattices: two-dimensional rotating and accordion lattices for ultracold atoms,'' Opt. Express 16, 16977-16983 (2008) [0pt] [2] J. H. Huckans, I. B. Spielman, B. Laburthe Tolra, W. D. Phillips, and J. V. Porto, Quantum and Classical Dynamics of a BEC in a Large-Period Optical Lattice, arXiv:0901.1386v1
Quark eigenmodes and lattice QCD
NASA Astrophysics Data System (ADS)
Liu, Guofeng
In this thesis, we study a number of topics in lattice QCD through the low-lying quark eigenmodes in the domain wall fermion (DWF) formulation in the quenched approximation. Specifically, we present results for the chiral condensate measured from these eigenmodes; we investigate the QCD vacuum structure by looking at the correlation between the magnitude of the chirality density, |psi†(x)gamma5psi( x)|, and the normal density, psi†( x)psi(x), for these states; we study the behavior of DWF formulation at large quark masses by investigating the mass dependence of the eigenvalues of the physical four dimensional-states as well as the bulk, five-dimensional states.
Gluonic transversity from lattice QCD
NASA Astrophysics Data System (ADS)
Detmold, W.; Shanahan, P. E.
2016-07-01
We present an exploratory study of the gluonic structure of the ϕ meson using lattice QCD (LQCD). This includes the first investigation of gluonic transversity via the leading moment of the twist-2 double-helicity-flip gluonic structure function Δ (x ,Q2). This structure function only exists for targets of spin J ≥1 and does not mix with quark distributions at leading twist, thereby providing a particularly clean probe of gluonic degrees of freedom. We also explore the gluonic analogue of the Soffer bound which relates the helicity flip and nonflip gluonic distributions, finding it to be saturated at the level of 80%. This work sets the stage for more complex LQCD studies of gluonic structure in the nucleon and in light nuclei where Δ (x ,Q2) is an "exotic glue" observable probing gluons in a nucleus not associated with individual nucleons.
Defect solitons in photonic lattices.
Yang, Jianke; Chen, Zhigang
2006-02-01
Nonlinear defect modes (defect solitons) and their stability in one-dimensional photonic lattices with focusing saturable nonlinearity are investigated. It is shown that defect solitons bifurcate out from every infinitesimal linear defect mode. Low-power defect solitons are linearly stable in lower bandgaps but unstable in higher bandgaps. At higher powers, defect solitons become unstable in attractive defects, but can remain stable in repulsive defects. Furthermore, for high-power solitons in attractive defects, we found a type of Vakhitov-Kolokolov (VK) instability which is different from the usual VK instability based on the sign of the slope in the power curve. Lastly, we demonstrate that in each bandgap, in addition to defect solitons which bifurcate from linear defect modes, there is also an infinite family of other defect solitons which can be stable in certain parameter regimes. PMID:16605473
Entropy of unimodular lattice triangulations
NASA Astrophysics Data System (ADS)
Knauf, Johannes F.; Krüger, Benedikt; Mecke, Klaus
2015-02-01
Triangulations are important objects of study in combinatorics, finite element simulations and quantum gravity, where their entropy is crucial for many physical properties. Due to their inherent complex topological structure even the number of possible triangulations is unknown for large systems. We present a novel algorithm for an approximate enumeration which is based on calculations of the density of states using the Wang-Landau flat histogram sampling. For triangulations on two-dimensional integer lattices we achieve excellent agreement with known exact numbers of small triangulations as well as an improvement of analytical calculated asymptotics. The entropy density is C=2.196(3) consistent with rigorous upper and lower bounds. The presented numerical scheme can easily be applied to other counting and optimization problems.
Multigroup Reactor Lattice Cell Calculation
Energy Science and Technology Software Center (ESTSC)
1990-03-01
The Winfrith Improved Multigroup Scheme (WIMS), is a general code for reactor lattice cell calculations on a wide range of reactor systems. In particular, the code will accept rod or plate fuel geometries in either regular arrays or in clusters, and the energy group structure has been chosen primarily for thermal calculations. The basic library has been compiled with 14 fast groups, 13 resonance groups and 42 thermal groups, but the user is offered themore » choice of accurate solutions in many groups or rapid calculations in few groups. Temperature dependent thermal scattering matrices for a variety of scattering laws are available in the library for the principal moderators which include hydrogen, deuterium, graphite, beryllium and oxygen. WIMSD5 is a succesor version of WIMS-D/4.« less
Simple lattice model of macroevolution
NASA Astrophysics Data System (ADS)
Borkowski, Wojciech
2009-04-01
In future astrobiology, like in modern astrophysics, the numerical simulations can be a very important tool for proving theories. In this paper, I propose a simple lattice model of a multi-species ecosystem suitable for the study of emergent properties of macroevolution. Unlike the majority of ecological models, the number of species is not fixed - they emerge by "mutation" of existing species, then survive or go extinct depending on the balance between local ecological interactions. The Monte-Carlo numerical simulations show that this model is able to qualitatively reproduce phenomena that have been empirically observed, like the dependence between size of the isolated area and the number of species inhabiting there, primary production and species-diversity. The model allows also studying the causes of mass extinctions and more generally, repeatability, and the role of pure chance in macroevolution.
Optical lattices with micromechanical mirrors
Hammerer, K.; Stannigel, K.; Genes, C.; Zoller, P.; Treutlein, P.; Camerer, S.; Hunger, D.; Haensch, T. W.
2010-08-15
We investigate a setup where a cloud of atoms is trapped in an optical lattice potential of a standing-wave laser field which is created by retroreflection on a micromembrane. The membrane vibrations itself realize a quantum mechanical degree of freedom. We show that the center-of-mass mode of atoms can be coupled to the vibrational mode of the membrane in free space. Via laser cooling of atoms a significant sympathetic cooling effect on the membrane vibrations can be achieved. Switching off laser cooling brings the system close to a regime of strong coherent coupling. This setup provides a controllable segregation between the cooling and coherent dynamics regimes, and allows one to keep the membrane in a cryogenic environment and atoms at a distance in a vacuum chamber.
On lattice chiral gauge theories
NASA Technical Reports Server (NTRS)
Maiani, L.; Rossi, G. C.; Testa, M.
1991-01-01
The Smit-Swift-Aoki formulation of a lattice chiral gauge theory is presented. In this formulation the Wilson and other non invariant terms in the action are made gauge invariant by the coupling with a nonlinear auxilary scalar field, omega. It is shown that omega decouples from the physical states only if appropriate parameters are tuned so as to satisfy a set of BRST identities. In addition, explicit ghost fields are necessary to ensure decoupling. These theories can give rise to the correct continuum limit. Similar considerations apply to schemes with mirror fermions. Simpler cases with a global chiral symmetry are discussed and it is shown that the theory becomes free at decoupling. Recent numerical simulations agree with those considerations.
Furman, M.A.
2002-06-19
This is a summary of the talks presented in Session III ''Simulations of Electron-Cloud Build Up'' of the Mini-Workshop on Electron-Cloud Simulations for Proton and Positron Beams ECLOUD-02, held at CERN, 15-18 April 2002.
ERIC Educational Resources Information Center
Ditlea, Steve
1982-01-01
Describes and evaluates the features, performance, peripheral devices, available software, and capabilities of the Apple III microcomputer. The computer's operating system, its hardware, and the commercially produced software it accepts are discussed. Specific applications programs for financial planning, accounting, and word processing are…
ERIC Educational Resources Information Center
Envirometrics, Inc., Washington, DC.
CITY III is a computer-assisted simulation game which allows the participants to make decisions affecting various aspects of the economic, governmental, and social sectors of a simulated urban area. The game director selects one of five possible starting city configurations, may set a number of conditions in the city before the start of play, and…
Expression and crystallization of a soluble form of Drosophila fasciclin III.
Strong, R K; Vaughn, D E; Bjorkman, P J; Snow, P M
1994-08-19
A truncated form of Drosophila fasciclin III has been engineered by site-directed mutagenesis. Secreted fasciclin III is expressed at 35 to 40 mg/l in insect cells with baculovirus carrying the recombinant gene. Single crystals of purified soluble fasciclin III have been grown by vapor diffusion versus polyethylene glycol 8000/sodium citrate at low pH. The space group is P6(1)22 or its enantiomorph P6(5)22, with unit cell dimensions a = b = 140 A, c = 260 A. Cryo-preserved crystals diffract to reciprocal lattice spacings beyond 3.0 A. PMID:8064861
NASA Astrophysics Data System (ADS)
Li, Shuli; Yan, Weigen
2016-06-01
In this work, we obtain explicit expression of the number of close-packed dimers (perfect matchings) of the 33 .42 lattice with cylindrical boundary condition. Particularly, we show that the entropy of 33 .42 lattice is the same for cylindrical and toroidal boundary conditions.
Results and Frontiers in Lattice Baryon Spectroscopy
John Bulava; Robert Edwards; George Fleming; K.Jimmy Juge; Adam C. Lichtl; Nilmani Mathur; Colin Morningstar; David Richards; Stephen J. Wallace
2007-06-16
The Lattice Hadron Physics Collaboration (LHPC) baryon spectroscopy effort is reviewed. To date the LHPC has performed exploratory Lattice QCD calculations of the low-lying spectrum of Nucleon and Delta baryons. These calculations demonstrate the effectiveness of our method by obtaining the masses of an unprecedented number of excited states with definite quantum numbers. Future work of the project is outlined.
Results and Frontiers in Lattice Baryon Spectroscopy
Bulava, John; Morningstar, Colin; Edwards, Robert; Richards, David; Fleming, George; Juge, K. Jimmy; Lichtl, Adam C.; Mathur, Nilmani; Wallace, Stephen J.
2007-10-26
The Lattice Hadron Physics Collaboration (LHPC) baryon spectroscopy effort is reviewed. To date the LHPC has performed exploratory Lattice QCD calculations of the low-lying spectrum of Nucleon and Delta baryons. These calculations demonstrate the effectiveness of our method by obtaining the masses of an unprecedented number of excited states with definite quantum numbers. Future work of the project is outlined.
LHC Phenomenology and Lattice Strong Dynamics
NASA Astrophysics Data System (ADS)
Fleming, G. T.
2013-03-01
While the LHC experimentalists work to find evidence of physics beyond the standard model, lattice gauge theorists are working as well to characterize the range of possible phenomena in strongly-coupled models of electroweak symmetry breaking. I will summarize the current progress of the Lattice Strong Dynamics (LSD) collaboration on the flavor dependence of SU(3) gauge theories.
Ultracold quantum gases in triangular optical lattices
NASA Astrophysics Data System (ADS)
Becker, C.; Soltan-Panahi, P.; Kronjäger, J.; Dörscher, S.; Bongs, K.; Sengstock, K.
2010-06-01
Over recent years, exciting developments in the field of ultracold atoms confined in optical lattices have led to numerous theoretical proposals devoted to the quantum simulation of problems e.g. known from condensed matter physics. Many of those ideas demand experimental environments with non-cubic lattice geometries. In this paper, we report on the implementation of a versatile three-beam lattice allowing for the generation of triangular as well as hexagonal optical lattices. As an important step, the superfluid-Mott insulator (SF-MI) quantum phase transition has been observed and investigated in detail in this lattice geometry for the first time. In addition to this, we study the physics of spinor Bose-Einstein condensates (BEC) in the presence of the triangular optical lattice potential, especially spin changing dynamics across the SF-MI transition. Our results suggest that, below the SF-MI phase transition, a well-established mean-field model describes the observed data when renormalizing the spin-dependent interaction. Interestingly, this opens up new perspectives for a lattice-driven tuning of a spin dynamics resonance occurring through the interplay of the quadratic Zeeman effect and spin-dependent interaction. Finally, we discuss further lattice configurations that can be realized with our setup.
Quantum nonlinear Schrodinger equation on a lattice
Bogolyubov, N.M.; Korepin, V.E.
1986-09-01
A local Hamiltonian is constructed for the nonlinear Schrodinger equation on a lattice in both the classical and the quantum variants. This Hamiltonian is an explicit elementary function of the local Bose fields. The lattice model possesses the same structure of the action-angle variables as the continuous model.
The Chroma Software System for Lattice QCD
Robert Edwards; Balint Joo
2004-06-01
We describe aspects of the Chroma software system for lattice QCD calculations. Chroma is an open source C++ based software system developed using the software infrastructure of the US SciDAC initiative. Chroma interfaces with output from the BAGEL assembly generator for optimized lattice fermion kernels on some architectures. It can be run on workstations, clusters and the QCDOC supercomputer.
A lattice formulation of chiral gauge theories
Bodwin, G.T.
1996-08-01
We present a method for implementing gauge theories of chiral fermions on the lattice. Discussed topics include: the lattice as a UV regulator, a chiral QED model, modification of the fermion determinant, large gauge-field momenta, and a non-perturbative problem.
Lattice Boltzmann equation for relativistic quantum mechanics.
Succi, Sauro
2002-03-15
Relativistic versions of the quantum lattice Boltzmann equation are discussed. It is shown that the inclusion of nonlinear interactions requires the standard collision operator to be replaced by a pair of dynamic fields coupling to the relativistic wave function in a way which can be described by a multicomponent complex lattice Boltzmann equation. PMID:16210189
Wave propagation on a random lattice
Sahlmann, Hanno
2010-09-15
Motivated by phenomenological questions in quantum gravity, we consider the propagation of a scalar field on a random lattice. We describe a procedure to calculate the dispersion relation for the field by taking a limit of a periodic lattice. We use this to calculate the lowest order coefficients of the dispersion relation for a specific one-dimensional model.
Recent advances in lattice Boltzmann methods
Chen, S.; Doolen, G.D.; He, X.; Nie, X.; Zhang, R.
1998-12-31
In this paper, the authors briefly present the basic principles of lattice Boltzmann method and summarize recent advances of the method, including the application of the lattice Boltzmann method for fluid flows in MEMS and simulation of the multiphase mixing and turbulence.
Finite-difference lattice-Boltzmann methods for binary fluids.
Xu, Aiguo
2005-06-01
We investigate two-fluid Bhatnagar-Gross-Krook (BGK) kinetic methods for binary fluids. The developed theory works for asymmetric as well as symmetric systems. For symmetric systems it recovers Sirovich's theory and is summarized in models A and B. For asymmetric systems it contributes models C, D, and E which are especially useful when the total masses and/or local temperatures of the two components are greatly different. The kinetic models are discretized based on an octagonal discrete velocity model. The discrete-velocity kinetic models and the continuous ones are required to describe the same hydrodynamic equations. The combination of a discrete-velocity kinetic model and an appropriate finite-difference scheme composes a finite-difference lattice Boltzmann method. The validity of the formulated methods is verified by investigating (i) uniform relaxation processes, (ii) isothermal Couette flow, and (iii) diffusion behavior. PMID:16089910
Mighell, Alan D.
2001-01-01
In theory, physical crystals can be represented by idealized mathematical lattices. Under appropriate conditions, these representations can be used for a variety of purposes such as identifying, classifying, and understanding the physical properties of materials. Critical to these applications is the ability to construct a unique representation of the lattice. The vital link that enabled this theory to be realized in practice was provided by the 1970 paper on the determination of reduced cells. This seminal paper led to a mathematical approach to lattice analysis initially based on systematic reduction procedures and the use of standard cells. Subsequently, the process evolved to a matrix approach based on group theory and linear algebra that offered a more abstract and powerful way to look at lattices and their properties. Application of the reduced cell to both database work and laboratory research at NIST was immediately successful. Currently, this cell and/or procedures based on reduction are widely and routinely used by the general scientific community: (i) for calculating standard cells for the reporting of crystalline materials, (ii) for classifying materials, (iii) in crystallographic database work (iv) in routine x-ray and neutron diffractometry, and (v) in general crystallographic research. Especially important is its use in symmetry determination and in identification. The focus herein is on the role of the reduced cell in lattice symmetry determination.
A mathematical model of collagen lattice contraction
Dallon, J. C.; Evans, E. J.; Ehrlich, H. Paul
2014-01-01
Two mathematical models for fibroblast–collagen interaction are proposed which reproduce qualitative features of fibroblast-populated collagen lattice contraction. Both models are force based and model the cells as individual entities with discrete attachment sites; however, the collagen lattice is modelled differently in each model. In the collagen lattice model, the lattice is more interconnected and formed by triangulating nodes to form the fibrous structure. In the collagen fibre model, the nodes are not triangulated, are less interconnected, and the collagen fibres are modelled as a string of nodes. Both models suggest that the overall increase in stress of the lattice as it contracts is not the cause of the reduced rate of contraction, but that the reduced rate of contraction is due to inactivation of the fibroblasts. PMID:25142520
Synthetic magnetic fluxes on the honeycomb lattice
Gorecka, Agnieszka; Gremaud, Benoit; Miniatura, Christian
2011-08-15
We devise experimental schemes that are able to mimic uniform and staggered magnetic fluxes acting on ultracold two-electron atoms, such as ytterbium atoms, propagating in a honeycomb lattice. The atoms are first trapped into two independent state-selective triangular lattices and then further exposed to a suitable configuration of resonant Raman laser beams. These beams induce hops between the two triangular lattices and make atoms move in a honeycomb lattice. Atoms traveling around each unit cell of this honeycomb lattice pick up a nonzero phase. In the uniform case, the artificial magnetic flux sustained by each cell can reach about two flux quanta, thereby realizing a cold-atom analog of the Harper model with its notorious Hofstadter's butterfly structure. Different condensed-matter phenomena such as the relativistic integer and fractional quantum Hall effects, as observed in graphene samples, could be targeted with this scheme.
Marin, E.; Tomas, R.; Bambade, P.; Okugi, T.; Tauchi, T.; Terunuma, N.; Urakawa, J.; Seryi, A.; White, G.; Woodley, M.; /SLAC
2011-12-09
The current status for the ATF2 Nominal and Ultra-low {beta}* lattices are presented in this paper. New lattice designs have been obtained in order to minimise the impact of the last interpretation of multipole measurements that have been included into the model. However, the new ATF2 Ultra-low design is not able to recover the expected vertical beam size at the IP with the current magnet distribution. Therefore, different quadrupole sorting have been studied. A significant gain is evident for the ATF2 Ultra-low lattice when sorting the magnets according to the skew-sextupolar components. The ATF2 Nominal lattice is also expected to benefit from the new sorting. Tuning results of the new ATF2 Ultra-low lattice under realistic imperfections are also reported.
Ising antiferromagnet on the Archimedean lattices.
Yu, Unjong
2015-06-01
Geometric frustration effects were studied systematically with the Ising antiferromagnet on the 11 Archimedean lattices using the Monte Carlo methods. The Wang-Landau algorithm for static properties (specific heat and residual entropy) and the Metropolis algorithm for a freezing order parameter were adopted. The exact residual entropy was also found. Based on the degree of frustration and dynamic properties, ground states of them were determined. The Shastry-Sutherland lattice and the trellis lattice are weakly frustrated and have two- and one-dimensional long-range-ordered ground states, respectively. The bounce, maple-leaf, and star lattices have the spin ice phase. The spin liquid phase appears in the triangular and kagome lattices. PMID:26172675
Quantum transport in d-dimensional lattices
Manzano, Daniel; Chuang, Chern; Cao, Jianshu
2016-04-28
We show that both fermionic and bosonic uniform d-dimensional lattices can be reduced to a set of independent one-dimensional chains. This reduction leads to the expression for ballistic energy fluxes in uniform fermionic and bosonic lattices. By the use of the Jordan–Wigner transformation we can extend our analysis to spin lattices, proving the coexistence of both ballistic and non-ballistic subspaces in any dimension and for any system size. Lastly, we then relate the nature of transport to the number of excitations in the homogeneous spin lattice, indicating that a single excitation always propagates ballistically and that the non-ballistic behaviour ofmore » uniform spin lattices is a consequence of the interaction between different excitations.« less
Counting lattice animals in high dimensions
NASA Astrophysics Data System (ADS)
Luther, Sebastian; Mertens, Stephan
2011-09-01
We present an implementation of Redelemeier's algorithm for the enumeration of lattice animals in high-dimensional lattices. The implementation is lean and fast enough to allow us to extend the existing tables of animal counts, perimeter polynomials and series expansion coefficients in d-dimensional hypercubic lattices for 3 <= d <= 10. From the data we compute formulae for perimeter polynomials for lattice animals of size n <= 11 in arbitrary dimension d. When amended by combinatorial arguments, the new data suffice to yield explicit formulae for the number of lattice animals of size n <= 14 and arbitrary d. We also use the enumeration data to compute numerical estimates for growth rates and exponents in high dimensions that agree very well with Monte Carlo simulations and recent predictions from field theory.
Quantum transport in d-dimensional lattices
NASA Astrophysics Data System (ADS)
Manzano, Daniel; Chuang, Chern; Cao, Jianshu
2016-04-01
We show that both fermionic and bosonic uniform d-dimensional lattices can be reduced to a set of independent one-dimensional chains. This reduction leads to the expression for ballistic energy fluxes in uniform fermionic and bosonic lattices. By the use of the Jordan–Wigner transformation we can extend our analysis to spin lattices, proving the coexistence of both ballistic and non-ballistic subspaces in any dimension and for any system size. We then relate the nature of transport to the number of excitations in the homogeneous spin lattice, indicating that a single excitation always propagates ballistically and that the non-ballistic behaviour of uniform spin lattices is a consequence of the interaction between different excitations.
Lattice kinetic simulation of nonisothermal magnetohydrodynamics.
Chatterjee, Dipankar; Amiroudine, Sakir
2010-06-01
In this paper, a lattice kinetic algorithm is presented to simulate nonisothermal magnetohydrodynamics in the low-Mach number incompressible limit. The flow and thermal fields are described by two separate distribution functions through respective scalar kinetic equations and the magnetic field is governed by a vector distribution function through a vector kinetic equation. The distribution functions are only coupled via the macroscopic density, momentum, magnetic field, and temperature computed at the lattice points. The novelty of the work is the computation of the thermal field in conjunction with the hydromagnetic fields in the lattice Boltzmann framework. A 9-bit two-dimensional (2D) lattice scheme is used for the numerical computation of the hydrodynamic and thermal fields, whereas the magnetic field is simulated in a 5-bit 2D lattice. Simulation of Hartmann flow in a channel provides excellent agreement with corresponding analytical results. PMID:20866540
Ising antiferromagnet on the Archimedean lattices
NASA Astrophysics Data System (ADS)
Yu, Unjong
2015-06-01
Geometric frustration effects were studied systematically with the Ising antiferromagnet on the 11 Archimedean lattices using the Monte Carlo methods. The Wang-Landau algorithm for static properties (specific heat and residual entropy) and the Metropolis algorithm for a freezing order parameter were adopted. The exact residual entropy was also found. Based on the degree of frustration and dynamic properties, ground states of them were determined. The Shastry-Sutherland lattice and the trellis lattice are weakly frustrated and have two- and one-dimensional long-range-ordered ground states, respectively. The bounce, maple-leaf, and star lattices have the spin ice phase. The spin liquid phase appears in the triangular and kagome lattices.
Lattice Boltzmann modeling of phonon transport
NASA Astrophysics Data System (ADS)
Guo, Yangyu; Wang, Moran
2016-06-01
A novel lattice Boltzmann scheme is proposed for phonon transport based on the phonon Boltzmann equation. Through the Chapman-Enskog expansion, the phonon lattice Boltzmann equation under the gray relaxation time approximation recovers the classical Fourier's law in the diffusive limit. The numerical parameters in the lattice Boltzmann model are therefore rigorously correlated to the bulk material properties. The new scheme does not only eliminate the fictitious phonon speed in the diagonal direction of a square lattice system in the previous lattice Boltzmann models, but also displays very robust performances in predicting both temperature and heat flux distributions consistent with analytical solutions for diverse numerical cases, including steady-state and transient, macroscale and microscale, one-dimensional and multi-dimensional phonon heat transport. This method may provide a powerful numerical tool for deep studies of nonlinear and nonlocal heat transports in nanosystems.
A lattice approach to spinorial quantum gravity
NASA Technical Reports Server (NTRS)
Renteln, Paul; Smolin, Lee
1989-01-01
A new lattice regularization of quantum general relativity based on Ashtekar's reformulation of Hamiltonian general relativity is presented. In this form, quantum states of the gravitational field are represented within the physical Hilbert space of a Kogut-Susskind lattice gauge theory. The gauge field of the theory is a complexified SU(2) connection which is the gravitational connection for left-handed spinor fields. The physical states of the gravitational field are those which are annihilated by additional constraints which correspond to the four constraints of general relativity. Lattice versions of these constraints are constructed. Those corresponding to the three-dimensional diffeomorphism generators move states associated with Wilson loops around on the lattice. The lattice Hamiltonian constraint has a simple form, and a correspondingly simple interpretation: it is an operator which cuts and joins Wilson loops at points of intersection.
Trapping Rydberg Atoms in an Optical Lattice
Anderson, S. E.; Younge, K. C.; Raithel, G.
2011-12-23
Rubidium Rydberg atoms are laser excited and subsequently trapped in a one-dimensional optical lattice (wavelength 1064 nm). Efficient trapping is achieved by a lattice inversion immediately after laser excitation using an electro-optic technique. The trapping efficiency is probed via analysis of the trap-induced shift of the two-photon microwave transition 50S{yields}51S. The inversion technique allows us to reach a trapping efficiency of 90%. The dependence of the efficiency on the timing of the lattice inversion and on the trap laser power is studied. The dwell time of 50D{sub 5/2} Rydberg atoms in the lattice is analyzed using lattice-induced photoionization.
Fast Lattice Monte Carlo Simulations of Polymers
NASA Astrophysics Data System (ADS)
Wang, Qiang; Zhang, Pengfei
2014-03-01
The recently proposed fast lattice Monte Carlo (FLMC) simulations (with multiple occupancy of lattice sites (MOLS) and Kronecker δ-function interactions) give much faster/better sampling of configuration space than both off-lattice molecular simulations (with pair-potential calculations) and conventional lattice Monte Carlo simulations (with self- and mutual-avoiding walk and nearest-neighbor interactions) of polymers.[1] Quantitative coarse-graining of polymeric systems can also be performed using lattice models with MOLS.[2] Here we use several model systems, including polymer melts, solutions, blends, as well as confined and/or grafted polymers, to demonstrate the great advantages of FLMC simulations in the study of equilibrium properties of polymers.
NASA Technical Reports Server (NTRS)
1969-01-01
The Hyper III was a full-scale lifting-body remotely piloted research vehicle (RPRV) built at what was then the NASA Flight Research Center located at Edwards Air Force Base in Southern California. The Flight Research Center (FRC--as Dryden was named from 1959 until 1976) already had experience with testing small-scale aircraft using model-airplane techniques, but the first true remotely piloted research vehicle was the Hyper III, which flew only once in December 1969. At that time, the Center was engaged in flight research with a variety of reentry shapes called lifting bodies, and there was a desire both to expand the flight research experience with maneuverable reentry vehicles, including a high-performance, variable-geometry craft, and to investigate a remotely piloted flight research technique that made maximum use of a research pilot's skill and experience by placing him 'in the loop' as if he were in the cockpit. (There have been, as yet, no female research pilots assigned to Dryden.) The Hyper III as originally conceived was a stiletto-shaped lifting body that had resulted from a study at NASA's Langley Research Center in Hampton, Virginia. It was one of a number of hypersonic, cross-range reentry vehicles studied at Langley. (Hypersonic means Mach 5--five times the speed of sound--or faster; cross-range means able to fly a considerable distance to the left or right of the initial reentry path.) The FRC added a small, deployable, skewed wing to compensate for the shape's extremely low glide ratio. Shop personnel built the 32-foot-long Hyper III and covered its tubular frame with dacron, aluminum, and fiberglass, for about $6,500. Hyper III employed the same '8-ball' attitude indicator developed for control-room use when flying the X-15, two model-airplane receivers to command the vehicle's hydraulic controls, and a telemetry system (surplus from the X-15 program) to transmit 12 channels of data to the ground not only for display and control but for data
Toward a realistic low-field SSC lattice
Heifets, S.
1985-10-01
Three six-fold lattices for 3 T superferric SSC have been generated at TAC. The program based on the first order canonical transformation was used to compare lattices. On this basis the realistic race-track lattices were generated.
Some physical and chemical indices of the Union Jack lattice
NASA Astrophysics Data System (ADS)
Li, Shuli; Yan, Weigen; Tian, Tao
2015-02-01
The Union Jack lattice is the dual lattice of the 4.8.8 lattice. The quantum spin model with frustration and the Ising model on the Union Jack lattice have been studied extensively by physicists. In this paper, we derive the spectrum and Laplacian spectrum of the Union Jack lattice with toroidal boundary condition. As applications, we obtain the formulae of the number of spanning trees, the energy, and the Kirchhoff index of the Union Jack lattice with toroidal boundary condition.
Lee, Pei-Chung
2015-01-01
Type III secretion systems are complex nanomachines that export proteins from the bacterial cytoplasm across the cell envelope in a single step. They are at the core of the machinery used to assemble the bacterial flagellum, and the needle complex many Gram-negative pathogens use to inject effector proteins into host cells and cause disease. Several models have been put forward to explain how this export is energized, and the mechanism has been the subject of considerable debate. Here we present an overview of these models and discuss their relative merits. Recent evidence suggests that the proton motive force is the primary energy source for type III secretion, although contribution from refolding of secreted proteins has not been ruled out. The mechanism, by which the proton motive force is converted to protein export, remains enigmatic. PMID:25701111
Cranial mononeuropathy III - diabetic type
... gov/ency/article/000692.htm Cranial mononeuropathy III - diabetic type To use the sharing features on this page, please enable JavaScript. Cranial mononeuropathy III -- diabetic type -- is usually a complication of diabetes that causes ...
New faces of the familiar clathrin lattice.
Wilbur, Jeremy D; Hwang, Peter K; Brodsky, Frances M
2005-04-01
The clathrin triskelion self-assembles into a lattice that coats transport vesicles participating in several key membrane traffic pathways. A new model of a clathrin lattice at approximately 8 angstrom resolution, generated by Fotin et al. (Nature 2004;432:573) confirmed the basic structural features of clathrin that were defined over many years of biochemical and structural analysis. In addition, new structural features of the clathrin trimerization domain were modelled for the first time, and the predictions correlated well with previous biochemical studies. A second model, placing auxilin within the lattice suggested a possible lattice contact targeted during lattice disassembly (Fotin et al. Nature 2004;432:649). This contact predicts interactions of the newly modelled trimerization domain with a newly defined extension of the clathrin triskelion, the ankle domain. These aspects of the new models were emphasized in the published reports describing them and in recent commentary (Brodsky, Nature 2004;432:568). Also emerging from the new models is a better picture of how the clathrin structure is distributed throughout the lattice, allowing the first predictions of interacting molecular interfaces contributing to contacts in the assembled lattice. The focus of this interchange is to emphasize these additional features revealed by the recently published models from Fotin and colleagues. PMID:15752139
Dynamic Behavior of Engineered Lattice Materials
NASA Astrophysics Data System (ADS)
Hawreliak, J. A.; Lind, J.; Maddox, B.; Barham, M.; Messner, M.; Barton, N.; Jensen, B. J.; Kumar, M.
2016-06-01
Additive manufacturing (AM) is enabling the fabrication of materials with engineered lattice structures at the micron scale. These mesoscopic structures fall between the length scale associated with the organization of atoms and the scale at which macroscopic structures are constructed. Dynamic compression experiments were performed to study the emergence of behavior owing to the lattice periodicity in AM materials on length scales that approach a single unit cell. For the lattice structures, both bend and stretch dominated, elastic deflection of the structure was observed ahead of the compaction of the lattice, while no elastic deformation was observed to precede the compaction in a stochastic, random structure. The material showed lattice characteristics in the elastic response of the material, while the compaction was consistent with a model for compression of porous media. The experimental observations made on arrays of 4 × 4 × 6 lattice unit cells show excellent agreement with elastic wave velocity calculations for an infinite periodic lattice, as determined by Bloch wave analysis, and finite element simulations.
Duality analysis on random planar lattices.
Ohzeki, Masayuki; Fujii, Keisuke
2012-11-01
The conventional duality analysis is employed to identify a location of a critical point on a uniform lattice without any disorder in its structure. In the present study, we deal with the random planar lattice, which consists of the randomized structure based on the square lattice. We introduce the uniformly random modification by the bond dilution and contraction on a part of the unit square. The random planar lattice includes the triangular and hexagonal lattices in extreme cases of a parameter to control the structure. A modern duality analysis fashion with real-space renormalization is found to be available for estimating the location of the critical points with a wide range of the randomness parameter. As a simple test bed, we demonstrate that our method indeed gives several critical points for the cases of the Ising and Potts models and the bond-percolation thresholds on the random planar lattice. Our method leads to not only such an extension of the duality analyses on the classical statistical mechanics but also a fascinating result associated with optimal error thresholds for a class of quantum error correction code, the surface code on the random planar lattice, which is known as a skillful technique to protect the quantum state. PMID:23214752
Dynamic Behavior of Engineered Lattice Materials
Hawreliak, J. A.; Lind, J.; Maddox, B.; Barham, M.; Messner, M.; Barton, N.; Jensen, B. J.; Kumar, M.
2016-01-01
Additive manufacturing (AM) is enabling the fabrication of materials with engineered lattice structures at the micron scale. These mesoscopic structures fall between the length scale associated with the organization of atoms and the scale at which macroscopic structures are constructed. Dynamic compression experiments were performed to study the emergence of behavior owing to the lattice periodicity in AM materials on length scales that approach a single unit cell. For the lattice structures, both bend and stretch dominated, elastic deflection of the structure was observed ahead of the compaction of the lattice, while no elastic deformation was observed to precede the compaction in a stochastic, random structure. The material showed lattice characteristics in the elastic response of the material, while the compaction was consistent with a model for compression of porous media. The experimental observations made on arrays of 4 × 4 × 6 lattice unit cells show excellent agreement with elastic wave velocity calculations for an infinite periodic lattice, as determined by Bloch wave analysis, and finite element simulations. PMID:27321697
Dynamic Behavior of Engineered Lattice Materials.
Hawreliak, J A; Lind, J; Maddox, B; Barham, M; Messner, M; Barton, N; Jensen, B J; Kumar, M
2016-01-01
Additive manufacturing (AM) is enabling the fabrication of materials with engineered lattice structures at the micron scale. These mesoscopic structures fall between the length scale associated with the organization of atoms and the scale at which macroscopic structures are constructed. Dynamic compression experiments were performed to study the emergence of behavior owing to the lattice periodicity in AM materials on length scales that approach a single unit cell. For the lattice structures, both bend and stretch dominated, elastic deflection of the structure was observed ahead of the compaction of the lattice, while no elastic deformation was observed to precede the compaction in a stochastic, random structure. The material showed lattice characteristics in the elastic response of the material, while the compaction was consistent with a model for compression of porous media. The experimental observations made on arrays of 4 × 4 × 6 lattice unit cells show excellent agreement with elastic wave velocity calculations for an infinite periodic lattice, as determined by Bloch wave analysis, and finite element simulations. PMID:27321697
Duality analysis on random planar lattices
NASA Astrophysics Data System (ADS)
Ohzeki, Masayuki; Fujii, Keisuke
2012-11-01
The conventional duality analysis is employed to identify a location of a critical point on a uniform lattice without any disorder in its structure. In the present study, we deal with the random planar lattice, which consists of the randomized structure based on the square lattice. We introduce the uniformly random modification by the bond dilution and contraction on a part of the unit square. The random planar lattice includes the triangular and hexagonal lattices in extreme cases of a parameter to control the structure. A modern duality analysis fashion with real-space renormalization is found to be available for estimating the location of the critical points with a wide range of the randomness parameter. As a simple test bed, we demonstrate that our method indeed gives several critical points for the cases of the Ising and Potts models and the bond-percolation thresholds on the random planar lattice. Our method leads to not only such an extension of the duality analyses on the classical statistical mechanics but also a fascinating result associated with optimal error thresholds for a class of quantum error correction code, the surface code on the random planar lattice, which is known as a skillful technique to protect the quantum state.
Modeling shocks in periodic lattice materials
NASA Astrophysics Data System (ADS)
Messner, Mark; Barham, Matthew; Barton, Nathan
2015-06-01
Periodic lattice materials have an excellent density-to-stiffness ratio, with the elastic stiffness of stretch dominated lattices scaling linearly with relative density. Recent developments in additive manufacturing techniques enable the use of lattice materials in situations where the response of the material to shock loading may become significant. Current continuum models do not describe the response of such lattice materials subject to shocks. This presentation details the development of continuum models suitable for representing shock propagation in periodic lattice materials, particularly focusing on the transition between elastic and plastic response. In the elastic regime, the material retains its periodic structure and equivalent continuum models of infinite, periodic truss structures accurately reproduce characteristics of stretch-dominated lattices. At higher velocities, the material tends to lose its initial lattice structure and begins to resemble a foam or a solid with dispersed voids. Capturing the transition between these regimes can be computationally challenging. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Scaling of Hamiltonian walks on fractal lattices.
Elezović-Hadzić, Suncica; Marcetić, Dusanka; Maletić, Slobodan
2007-07-01
We investigate asymptotical behavior of numbers of long Hamiltonian walks (HWs), i.e., self-avoiding random walks that visit every site of a lattice, on various fractal lattices. By applying an exact recursive technique we obtain scaling forms for open HWs on three-simplex lattice, Sierpinski gasket, and their generalizations: Given-Mandelbrot (GM), modified Sierpinski gasket (MSG), and n -simplex fractal families. For GM, MSG and n -simplex lattices with odd values of n , the number of open HWs Z(N), for the lattice with N>1 sites, varies as omega(N)}N(gamma). We explicitly calculate the exponent gamma for several members of GM and MSG families, as well as for n-simplices with n=3, 5, and 7. For n-simplex fractals with even n we find different scaling form: Z(N) approximately omega(N)mu(N1/d(f), where d(f) is the fractal dimension of the lattice, which also differs from the formula expected for homogeneous lattices. We discuss possible implications of our results on studies of real compact polymers. PMID:17677410
MBE growth technology for high quality strained III-V layers
NASA Technical Reports Server (NTRS)
Grunthaner, Frank J. (Inventor); Liu, John K. (Inventor); Hancock, Bruce R. (Inventor)
1990-01-01
The III-V films are grown on large automatically perfect terraces of III-V substrates which have a different lattice constant, with temperature and Group III and V arrival rates chosen to give a Group III element stable surface. The growth is pulsed to inhibit Group III metal accumulation of low temperature, and to permit the film to relax to equilibrium. The method of the invention: (1) minimizes starting step density on sample surface; (2) deposits InAs and GaAs using an interrupted growth mode (0.25 to 2 monolayers at a time); (3) maintains the instantaneous surface stoichiometry during growth (As-stable for GaAs, In-stable for InAs); and (4) uses time-resolved RHEED to achieve aspects (1) through (3).
Lattice-Mismatched GaAs/InGaAs Two-Junction Solar Cells by Direct Wafer Bonding
Tanabe, K.; Aiken, D. J.; Wanlass, M. W.; Morral, A. F.; Atwater, H. A.
2006-01-01
Direct bonded interconnect between subcells of a lattice-mismatched III-V compound multijunction cell would enable dislocation-free active regions by confining the defect network needed for lattice mismatch accommodation to tunnel junction interfaces, while metamorphic growth inevitably results in less design flexibility and lower material quality than is desirable. The first direct-bond interconnected multijunction solar cell, a two-terminal monolithic GaAs/InGaAs two-junction solar cell, is reported and demonstrates viability of direct wafer bonding for solar cell applications. The tandem cell open-circuit voltage was approximately the sum of the subcell open-circuit voltages. This achievement shows direct bonding enables us to construct lattice-mismatched III-V multijunction solar cells and is extensible to an ultrahigh efficiency InGaP/GaAs/InGaAsP/InGaAs four-junction cell by bonding a GaAs-based lattice-matched InGaP/GaAs subcell and an InP-based lattice-matched InGaAsP/InGaAs subcell. The interfacial resistance experimentally obtained for bonded GaAs/InP smaller than 0.10 Ohm-cm{sup 2} would result in a negligible decrease in overall cell efficiency of {approx}0.02%, under 1-sun illumination.
A Review of Nucleon Spin Calculations in Lattice QCD
Huey-Wen Lin
2009-08-01
We review recent progress on lattice calculations of nucleon spin structure, including the parton distribution functions, form factors, generalization parton distributions, and recent developments in lattice techniques.
NASA Astrophysics Data System (ADS)
Artymowicz, Pawel
2004-03-01
Migration type IIIMigration of objects embedded in disks (and the accompanying eccentricity evolution) is becoming a major theme in planetary system formation.The underlying physics can be distilled into the notion of disk-planet coupling via Lindblad resonances, which launch waves, sometimes spectacular spiral shock waves in gas disks. The wave pattern exchanges angular momentum with the planet. That causes (i) migration, (ii) eccentricity evolution, and (iii) gap opening by sufficiently massive planets.A competing source of disk-planet interaction, the corotationaltorques, are much less conspicuous (corotation does not produce easilydetectable waves, as galaxy observers can attest) and have often been missed in the analysis of planet migration. If spiral waves are like waves at Goleta beach, then the corotation acts more like a stealthy riptide. Corotationalflows lie at the basis of a new, surprisingly rapid, mode of migration (type III),superseding the standard type II migration (with a gap), and revising the speed of type I migration (without a gap). The talk will contain results obtained at KITP, e.g., an analytical derivation of da/dt in type III motion. It will be illustrated by videos of high-resolution numerical simulations obtained with different implementations of the Piecewise Parabolic Method hydrodynamics.
Anyonic braiding in optical lattices
Zhang, Chuanwei; Scarola, V. W.; Tewari, Sumanta; Das Sarma, S.
2007-01-01
Topological quantum states of matter, both Abelian and non-Abelian, are characterized by excitations whose wavefunctions undergo nontrivial statistical transformations as one excitation is moved (braided) around another. Topological quantum computation proposes to use the topological protection and the braiding statistics of a non-Abelian topological state to perform quantum computation. The enormous technological prospect of topological quantum computation provides new motivation for experimentally observing a topological state. Here, we explicitly work out a realistic experimental scheme to create and braid the Abelian topological excitations in the Kitaev model built on a tunable robust system, a cold atom optical lattice. We also demonstrate how to detect the key feature of these excitations: their braiding statistics. Observation of this statistics would directly establish the existence of anyons, quantum particles that are neither fermions nor bosons. In addition to establishing topological matter, the experimental scheme we develop here can also be adapted to a non-Abelian topological state, supported by the same Kitaev model but in a different parameter regime, to eventually build topologically protected quantum gates. PMID:18000038
Lee, Y.Y.; Barton, D.S.; Claus, J.; Cottingham, J.G.; Courant, E.D.; Danby, G.T.; Dell, G.F.; Forsyth, E.B.; Gupta, R.C.; Kats, J.
1987-01-01
The AGS Booster has three objectives. They are to increase the space charge limit of the AGS, to increase the intensity of the polarized proton beam by accumulating many linac pulses (since the intensity is limited by the polarized ion source), and to reaccelerate heavy ions from the BNL Tandem Van de Graaff before injection into the AGS. The machine is capable of accelerating protons at 7.5 Hertz from 200 MeV to 1.5 GeV or to lower final energies at faster repetition rates. The machine will also be able to accelerate heavy ions from as low as 1 MeV/nucleon to a magnetic rigidity as high as 17.6 Tesla-meters with a one second repetition rate. As an accumulator for polarized protons, the Booster should be able to store the protons at 200 MeV for several seconds. We expect that the Booster will increase the AGS proton intensity by a factor of four, polarized proton intensity by a factor of twenty to thirty, and will also enable the AGS to accelerate all species of heavy ions (at present the AGS heavy ion program is limited to the elements lighter than sulfur because it can only accelerate fully stripped ions). The construction project started in FY 1985 and is expected to be completed in 1989. The purpose of this paper is to provide a future reference for the AGS Booster lattice.
Performance comparisons of low emittance lattices
Delahaye, J.P.; Zisman, M.S.
1987-05-01
In this paper, the results of a performance analysis of several low emittance electron storage ring lattices provided by various members of the Lattice Working Group are presented. Altogether, four lattices were investigated. There are two different functions being considered for the low beam emittance rings discussed here. The first is to serve as a Damping Ring (DR), i.e., to provide the emittance damping required for a high energy linear collider. The second is to provide beams for a short wavelength Free Electron Laser (FEL), which is envisioned to operate in the wavelength region near 40 A.
Charmonium excited state spectrum in lattice QCD
Jozef Dudek; Robert Edwards; Nilmani Mathur; David Richards
2008-02-01
Working with a large basis of covariant derivative-based meson interpolating fields we demonstrate the feasibility of reliably extracting multiple excited states using a variational method. The study is performed on quenched anisotropic lattices with clover quarks at the charm mass. We demonstrate how a knowledge of the continuum limit of a lattice interpolating field can give additional spin-assignment information, even at a single lattice spacing, via the overlap factors of interpolating field and state. Excited state masses are systematically high with respect to quark potential model predictions and, where they exist, experimental states. We conclude that this is most likely a result of the quenched approximation.
Reactive Orthotropic Lattice Diffuser for Noise Reduction
NASA Technical Reports Server (NTRS)
Khorrami, Mehdi R. (Inventor)
2016-01-01
An orthotropic lattice structure interconnects porous surfaces of the flap with internal lattice-structured perforations to equalize the steady pressure field on the flap surfaces adjacent to the end and to reduce the amplitude of the fluctuations in the flow field near the flap end. The global communication that exists within all of the perforations provides the mechanism to lessen the pressure gradients experienced by the end portion of the flap. In addition to having diffusive effects (diffusing the incoming flow), the three-dimensional orthogonal lattice structure is also reactive (acoustic wave phase distortion) due to the interconnection of the perforations.
Thermometry via Light Shifts in Optical Lattices
NASA Astrophysics Data System (ADS)
McDonald, M.; McGuyer, B. H.; Iwata, G. Z.; Zelevinsky, T.
2015-01-01
For atoms or molecules in optical lattices, conventional thermometry methods are often unsuitable due to low particle numbers or a lack of cycling transitions. However, a differential spectroscopic light shift can map temperature onto the line shape with a low sensitivity to trap anharmonicity. We study narrow molecular transitions to demonstrate precise frequency-based lattice thermometry, as well as carrier cooling. This approach should be applicable down to nanokelvin temperatures. We also discuss how the thermal light shift can affect the accuracy of optical lattice clocks.
Tracking results using a standard cell lattice
Gelfand, N.M.
1987-10-01
This is a summary of results obtained by tracking a single particle through a lattice composed of a r.f. cavity and standard FODO cells. The lattice also includes two families of sextupoles for controlling the chromaticity. The parameters of the cells, i.e. their length and phase advance, closely resemble those of the Fermilab Main Ring or the Tevatron. We therefore have a model lattice which is similar to that of those accelerators but without the straight sections present in the actual machines. It is hoped that the simplified model used will exhibit the salient features of the actual accelerator but will be simpler to understand. 8 figs., 1 tab.
Entropic lattice Boltzmann model for compressible flows.
Frapolli, N; Chikatamarla, S S; Karlin, I V
2015-12-01
We present a lattice Boltzmann model (LBM) that covers the entire range of fluid flows, from low Mach weakly compressible to transonic and supersonic flows. One of the most restrictive limitations of the lattice Boltzmann method, the low Mach number limit, is overcome here by three fundamental changes to the LBM scheme: use of an appropriately chosen multispeed lattice, accurate evaluation of the equilibrium, and the entropic relaxation for the collision. The range of applications is demonstrated through the simulation of a bow shock in front of an airfoil and the simulation of decaying compressible turbulence with shocklets. PMID:26764625
Continuum methods in lattice perturbation theory
Becher, Thomas G
2002-11-15
We show how methods of continuum perturbation theory can be used to simplify perturbative lattice calculations. We use the technique of asymptotic expansions to expand lattice loop integrals around the continuum limit. After the expansion, all nontrivial dependence on momenta and masses is encoded in continuum loop integrals and the only genuine lattice integrals left are tadpole integrals. Using integration-by-parts relations all of these can be expressed in terms of a small number of master integrals. Four master integrals are needed for bosonic one loop integrals, sixteen in QCD with Wilson or staggered fermions.
A lattice model for data display
NASA Technical Reports Server (NTRS)
Hibbard, William L.; Dyer, Charles R.; Paul, Brian E.
1994-01-01
In order to develop a foundation for visualization, we develop lattice models for data objects and displays that focus on the fact that data objects are approximations to mathematical objects and real displays are approximations to ideal displays. These lattice models give us a way to quantize the information content of data and displays and to define conditions on the visualization mappings from data to displays. Mappings satisfy these conditions if and only if they are lattice isomorphisms. We show how to apply this result to scientific data and display models, and discuss how it might be applied to recursively defined data types appropriate for complex information processing.
Entropic lattice Boltzmann model for compressible flows
NASA Astrophysics Data System (ADS)
Frapolli, N.; Chikatamarla, S. S.; Karlin, I. V.
2015-12-01
We present a lattice Boltzmann model (LBM) that covers the entire range of fluid flows, from low Mach weakly compressible to transonic and supersonic flows. One of the most restrictive limitations of the lattice Boltzmann method, the low Mach number limit, is overcome here by three fundamental changes to the LBM scheme: use of an appropriately chosen multispeed lattice, accurate evaluation of the equilibrium, and the entropic relaxation for the collision. The range of applications is demonstrated through the simulation of a bow shock in front of an airfoil and the simulation of decaying compressible turbulence with shocklets.
Application of model search to lattice theory.
Rose, M.; Wilkinson, K.; Mathematics and Computer Science
2001-08-01
We have used the first-order model-searching programs MACE and SEM to study various problems in lattice theory. First, we present a case study in which the two programs are used to examine the differences between the stages along the way from lattice theory to Boolean algebra. Second, we answer several questions posed by Norman Megill and Mladen Pavicic on ortholattices and orthomodular lattices. The questions from Megill and Pavicic arose in their study of quantum logics, which are being investigated in connection with proposed computing devices based on quantum mechanics. Previous questions of a similar nature were answered by McCune and MACE in [2].
XXIVth International Symposium on Lattice Field Theory
NASA Astrophysics Data System (ADS)
2006-12-01
Lattice 2006, the XXIV International Symposium on Lattice Field Theory, was held from July 23-28, 2006 at the Starr Pass Hotel near Tucson, Arizona, USA, hosted by the University of Arizona Physics Department. The scientific program contained 25 plenary session talks and 193 parallel session contributions (talks and posters). Topics in lattice QCD included: hadron spectroscopy; hadronic interactions and structure; algorithms, machines, and networks; chiral symmetry; QCD confinement and topology; quark masses, gauge couplings, and renormalization; electroweak decays and mixing; high temperature and density; and theoretical developments. Topics beyond QCD included large Nc, Higgs, SUSY, gravity, and strings.
NASA Astrophysics Data System (ADS)
Tsutaoka, Takanori; Tokunaga, Tomohito; Umeda, Takashi; Maehara, Toshinobu
2014-09-01
Demonstration of the diffraction patterns from the two-dimensional Bravais lattice has been studied by use of the two single line lattice grating sheets and a laser pointer. A variable two-dimensional lattice grating was prepared using two grating sheets which are closely attached to each other. The five types of two-dimensional Bravais lattices can be produced by adjusting the relative angle between two single line lattices. The light diffraction patterns from the two-dimensional Bravais lattices indicate the reciprocal lattices of these basic two-dimensional lattice structures.
NBS LATTICE: A program to analyze lattice relationships, version of summer, 1985
NASA Astrophysics Data System (ADS)
Himes, V. L.; Mighell, A. D.
1985-12-01
A FORTRAN program to analyze lattice relationships has been written and is available for distribution by the NBS Crystal Data Center. The present version of NBS *LATTICE performs several functions including: (1) the characterization and identification of unknown materials using lattice-formula matching techniques; (2) the calculation of the reduced cell of the lattice, and the calculation and reduction of specified derivative supercells and/or subcells (i.e., this program function calculates the standard cells which are useful in the determination of metric lattice symmetry in finding a matrix relating two unit cells, etc.); (3) unit cell transformations; and (4) matrix inversions. It is planned to incorporate additional functions in forthcoming versions of this program. Among others, these functions will include a matrix method to determine metric lattice symmetry and a technique to find a transformation matrix relating any two unit cells.
Bishop, R. F.; Li, P. H. Y.
2011-04-15
An approximation hierarchy, called the lattice-path-based subsystem (LPSUBm) approximation scheme, is described for the coupled-cluster method (CCM). It is applicable to systems defined on a regular spatial lattice. We then apply it to two well-studied prototypical (spin-(1/2) Heisenberg antiferromagnetic) spin-lattice models, namely, the XXZ and the XY models on the square lattice in two dimensions. Results are obtained in each case for the ground-state energy, the ground-state sublattice magnetization, and the quantum critical point. They are all in good agreement with those from such alternative methods as spin-wave theory, series expansions, quantum Monte Carlo methods, and the CCM using the alternative lattice-animal-based subsystem (LSUBm) and the distance-based subsystem (DSUBm) schemes. Each of the three CCM schemes (LSUBm, DSUBm, and LPSUBm) for use with systems defined on a regular spatial lattice is shown to have its own advantages in particular applications.
NASA Astrophysics Data System (ADS)
Bishop, R. F.; Li, P. H. Y.
2011-04-01
An approximation hierarchy, called the lattice-path-based subsystem (LPSUBm) approximation scheme, is described for the coupled-cluster method (CCM). It is applicable to systems defined on a regular spatial lattice. We then apply it to two well-studied prototypical (spin-(1)/(2) Heisenberg antiferromagnetic) spin-lattice models, namely, the XXZ and the XY models on the square lattice in two dimensions. Results are obtained in each case for the ground-state energy, the ground-state sublattice magnetization, and the quantum critical point. They are all in good agreement with those from such alternative methods as spin-wave theory, series expansions, quantum Monte Carlo methods, and the CCM using the alternative lattice-animal-based subsystem (LSUBm) and the distance-based subsystem (DSUBm) schemes. Each of the three CCM schemes (LSUBm, DSUBm, and LPSUBm) for use with systems defined on a regular spatial lattice is shown to have its own advantages in particular applications.
Analysis of quantum spin models on hyperbolic lattices and Bethe lattice
NASA Astrophysics Data System (ADS)
Daniška, Michal; Gendiar, Andrej
2016-04-01
The quantum XY, Heisenberg, and transverse field Ising models on hyperbolic lattices are studied by means of the tensor product variational formulation algorithm. The lattices are constructed by tessellation of congruent polygons with coordination number equal to four. The calculated ground-state energies of the XY and Heisenberg models and the phase transition magnetic field of the Ising model on the series of lattices are used to estimate the corresponding quantities of the respective models on the Bethe lattice. The hyperbolic lattice geometry induces mean-field-like behavior of the models. The ambition to obtain results on the non-Euclidean lattice geometries has been motivated by theoretical studies of the anti-de Sitter/conformal field theory correspondence.
Lattice Waves, Spin Waves, and Neutron Scattering
DOE R&D Accomplishments Database
Brockhouse, Bertram N.
1962-03-01
Use of neutron inelastic scattering to study the forces between atoms in solids is treated. One-phonon processes and lattice vibrations are discussed, and experiments that verified the existence of the quantum of lattice vibrations, the phonon, are reviewed. Dispersion curves, phonon frequencies and absorption, and models for dispersion calculations are discussed. Experiments on the crystal dynamics of metals are examined. Dispersion curves are presented and analyzed; theory of lattice dynamics is considered; effects of Fermi surfaces on dispersion curves; electron-phonon interactions, electronic structure influence on lattice vibrations, and phonon lifetimes are explored. The dispersion relation of spin waves in crystals and experiments in which dispersion curves for spin waves in Co-Fe alloy and magnons in magnetite were obtained and the reality of the magnon was demonstrated are discussed. (D.C.W)
Parton distributions from lattice QCD: an update
Detmold, W; Melnitchouk, W; Thomas, A W
2004-04-01
We review the extraction of parton distributions from their moments calculated in lattice QCD, focusing in particular on their extrapolation to the physical region. As examples, we consider both the unpolarized and polarized isovector parton distributions of the nucleon.
Optical vortex array in spatially varying lattice
NASA Astrophysics Data System (ADS)
Kapoor, Amit; Kumar, Manish; Senthilkumaran, P.; Joseph, Joby
2016-04-01
We present an experimental method based on a modified multiple beam interference approach to generate an optical vortex array arranged in a spatially varying lattice. This method involves two steps which are: numerical synthesis of a consistent phase mask by using two-dimensional integrated phase gradient calculations and experimental implementation of produced phase mask by utilizing a phase only spatial light modulator in an optical 4f Fourier filtering setup. This method enables an independent variation of the orientation and period of the vortex lattice. As working examples, we provide the experimental demonstration of various spatially variant optical vortex lattices. We further confirm the existence of optical vortices by formation of fork fringes. Such lattices may find applications in size dependent trapping, sorting, manipulation and photonic crystals.
Colloquium: Physics of optical lattice clocks
Derevianko, Andrei; Katori, Hidetoshi
2011-04-01
Recently invented and demonstrated optical lattice clocks hold great promise for improving the precision of modern time keeping. These clocks aim at the 10{sup -18} fractional accuracy, which translates into a clock that would neither lose nor gain a fraction of a second over an estimated age of the Universe. In these clocks, millions of atoms are trapped and interrogated simultaneously, dramatically improving clock stability. Here the principles of operation of these clocks are discussed and, in particular, a novel concept of magic trapping of atoms in optical lattices. Recently proposed microwave lattice clocks are also highlights and several applications that employ the optical lattice clocks as a platform for precision measurements and quantum information processing.
Ballistic Transport in Graphene Antidot Lattices.
Sandner, Andreas; Preis, Tobias; Schell, Christian; Giudici, Paula; Watanabe, Kenji; Taniguchi, Takashi; Weiss, Dieter; Eroms, Jonathan
2015-12-01
The bulk carrier mobility in graphene was shown to be enhanced in graphene-boron nitride heterostructures. However, nanopatterning graphene can add extra damage and drastically degrade the intrinsic properties by edge disorder. Here we show that graphene embedded into a heterostructure with hexagonal boron nitride (hBN) on both sides is protected during a nanopatterning step. In this way, we can prepare graphene-based antidot lattices where the high mobility is preserved. We report magnetotransport experiments in those antidot lattices with lattice periods down to 50 nm. We observe pronounced commensurability features stemming from ballistic orbits around one or several antidots. Due to the short lattice period in our samples, we can also explore the boundary between the classical and the quantum transport regime, as the Fermi wavelength of the electrons approaches the smallest length scale of the artificial potential. PMID:26598218
Nondestructive imaging of an ultracold lattice gas
NASA Astrophysics Data System (ADS)
Patil, Y. S.; Chakram, S.; Aycock, L. M.; Vengalattore, M.
2014-09-01
We demonstrate the nondestructive imaging of a lattice gas of ultracold bosons. Atomic fluorescence is induced in the simultaneous presence of degenerate Raman sideband cooling. The combined influence of these processes controllably cycles an atom between a dark state and a fluorescing state while eliminating heating and loss. Through spatially resolved sideband spectroscopy following the imaging sequence, we demonstrate the efficacy of this imaging technique in various regimes of lattice depth and fluorescence acquisition rate. Our work provides an important extension of quantum gas imaging to the nondestructive detection, control, and manipulation of atoms in optical lattices. In addition, our technique can also be extended to atomic species that are less amenable to molasses-based lattice imaging.
Lattice engineering through nanoparticle-DNA frameworks.
Tian, Ye; Zhang, Yugang; Wang, Tong; Xin, Huolin L; Li, Huilin; Gang, Oleg
2016-06-01
Advances in self-assembly over the past decade have demonstrated that nano- and microscale particles can be organized into a large diversity of ordered three-dimensional (3D) lattices. However, the ability to generate different desired lattice types from the same set of particles remains challenging. Here, we show that nanoparticles can be assembled into crystalline and open 3D frameworks by connecting them through designed DNA-based polyhedral frames. The geometrical shapes of the frames, combined with the DNA-assisted binding properties of their vertices, facilitate the well-defined topological connections between particles in accordance with frame geometry. With this strategy, different crystallographic lattices using the same particles can be assembled by introduction of the corresponding DNA polyhedral frames. This approach should facilitate the rational assembly of nanoscale lattices through the design of the unit cell. PMID:26901516
Random sequential adsorption on imprecise lattice.
Privman, Vladimir; Yan, Han
2016-06-28
We report a surprising result, established by numerical simulations and analytical arguments for a one-dimensional lattice model of random sequential adsorption, that even an arbitrarily small imprecision in the lattice-site localization changes the convergence to jamming from fast, exponential, to slow, power-law, with, for some parameter values, a discontinuous jump in the jamming coverage value. This finding has implications for irreversible deposition on patterned substrates with pre-made landing sites for particle attachment. We also consider a general problem of the particle (depositing object) size not an exact multiple of the lattice spacing, and the lattice sites themselves imprecise, broadened into allowed-deposition intervals. Regions of exponential vs. power-law convergence to jamming are identified, and certain conclusions regarding the jamming coverage are argued for analytically and confirmed numerically. PMID:27369530
Anyonization of lattice Chern-Simons theory
Eliezer, D.; Semenoff, G.W. )
1992-07-01
The authors formulate Hamiltonian lattice Chern-Simons theory which has the property that the Chern-Simons gauge fields of the theory can be eliminated by making matter fields multivalued operators with anyonic statistics. They prove that, when the statistics parameter is an odd integer so that the anyons are bosons, the ground state, which consists of a condensate of bound pairs of flux tubes and fermions, breaks phase invariance. The ensuing long-range order implies that the system is an unconventional superfluid. They formulate a condition which may be useful as a numerical signal for symmetry breaking in the ground state for any statistics parameter. They also discuss an exotic lattice Chern-Simons theory, which makes explicit the relation of anyons to framed knot invariants. They discuss various lattice representations of the Chern-Simons term and find the unique local lattice Chern-Simon term with the appropriate naive continuum limit, which permits anyonization.
Camera placement in integer lattices (extended abstract)
NASA Astrophysics Data System (ADS)
Pocchiola, Michel; Kranakis, Evangelos
1990-09-01
Techniques for studying an art gallery problem (the camera placement problem) in the infinite lattice (L sup d) of d tuples of integers are considered. A lattice point A is visible from a camera C positioned at a vertex of (L sup d) if A does not equal C and if the line segment joining A and C crosses no other lattice vertex. By using a combination of probabilistic, combinatorial optimization and algorithmic techniques the position they must occupy in the lattice (L sup d) in the order to maximize their visibility can be determined in polynomial time, for any given number s less than or equal to (5 sup d) of cameras. This improves previous results for s less than or equal to (3 sup d).
Strange Baryon Physics in Full Lattice QCD
Huey-Wen Lin
2007-11-01
Strange baryon spectra and form factors are key probes to study excited nuclear matter. The use of lattice QCD allows us to test the strength of the Standard Model by calculating strange baryon quantities from first principles.
Recent lattice QCD results on nucleon structure
Konstantinos Orginos
2006-07-01
I review recent developments in lattice calculations of nucleon structure. In particular, I cover the calculations of nucleon matrix elements related to generalized parton distribution functions, structure functions and form factors.
Regge calculus models of closed lattice universes
NASA Astrophysics Data System (ADS)
Liu, Rex G.; Williams, Ruth M.
2016-01-01
This paper examines the behavior of closed "lattice universes" wherein masses are distributed in a regular lattice on the Cauchy surfaces of closed vacuum universes. Such universes are approximated using a form of Regge calculus originally developed by Collins and Williams to model closed Friedmann-Lemaître-Robertson-Walker universes. We consider two types of lattice universes, one where all masses are identical to each other and another where one mass gets perturbed in magnitude. In the unperturbed universe, we consider the possible arrangements of the masses in the Regge Cauchy surfaces and demonstrate that the model will only be stable if each mass lies within some spherical region of convergence. We also briefly discuss the existence of Regge models that are dual to the ones we have considered. We then model a perturbed lattice universe and demonstrate that the model's evolution is well behaved, with the expansion increasing in magnitude as the perturbation is increased.
Visualization of 3D optical lattices
NASA Astrophysics Data System (ADS)
Lee, Hoseong; Clemens, James
2016-05-01
We describe the visualization of 3D optical lattices based on Sisyphus cooling implemented with open source software. We plot the adiabatic light shift potentials found by diagonalizing the effective Hamiltonian for the light shift operator. Our program incorporates a variety of atomic ground state configurations with total angular momentum ranging from j = 1 / 2 to j = 4 and a variety of laser beam configurations including the two-beam lin ⊥ lin configuration, the four-beam umbrella configuration, and four beams propagating in two orthogonal planes. In addition to visualizing the lattice the program also evaluates lattice parameters such as the oscillation frequency for atoms trapped deep in the wells. The program is intended to help guide experimental implementations of optical lattices.
Persistent superconductor currents in holographic lattices.
Iizuka, Norihiro; Ishibashi, Akihiro; Maeda, Kengo
2014-07-01
We consider a persistent superconductor current along the direction with no translational symmetry in a holographic gravity model. Incorporating a lattice structure into the model, we numerically construct novel solutions of hairy charged stationary black branes with momentum or rotation along the latticed direction. The lattice structure prevents the horizon from rotating, and the total momentum is only carried by matter fields outside the black brane horizon. This is consistent with the black hole rigidity theorem, and it suggests that in dual field theory with lattices, superconductor currents are made up of "composite" fields, rather than "fractionalized" degrees of freedom. We also show that our solutions are consistent with the superfluid hydrodynamics. PMID:25032917
Lattice engineering through nanoparticle-DNA frameworks
NASA Astrophysics Data System (ADS)
Tian, Ye; Zhang, Yugang; Wang, Tong; Xin, Huolin L.; Li, Huilin; Gang, Oleg
2016-06-01
Advances in self-assembly over the past decade have demonstrated that nano- and microscale particles can be organized into a large diversity of ordered three-dimensional (3D) lattices. However, the ability to generate different desired lattice types from the same set of particles remains challenging. Here, we show that nanoparticles can be assembled into crystalline and open 3D frameworks by connecting them through designed DNA-based polyhedral frames. The geometrical shapes of the frames, combined with the DNA-assisted binding properties of their vertices, facilitate the well-defined topological connections between particles in accordance with frame geometry. With this strategy, different crystallographic lattices using the same particles can be assembled by introduction of the corresponding DNA polyhedral frames. This approach should facilitate the rational assembly of nanoscale lattices through the design of the unit cell.
A multivariate CAR model for mismatched lattices.
Porter, Aaron T; Oleson, Jacob J
2014-10-01
In this paper, we develop a multivariate Gaussian conditional autoregressive model for use on mismatched lattices. Most current multivariate CAR models are designed for each multivariate outcome to utilize the same lattice structure. In many applications, a change of basis will allow different lattices to be utilized, but this is not always the case, because a change of basis is not always desirable or even possible. Our multivariate CAR model allows each outcome to have a different neighborhood structure which can utilize different lattices for each structure. The model is applied in two real data analysis. The first is a Bayesian learning example in mapping the 2006 Iowa Mumps epidemic, which demonstrates the importance of utilizing multiple channels of infection flow in mapping infectious diseases. The second is a multivariate analysis of poverty levels and educational attainment in the American Community Survey. PMID:25457598
Stability analysis of lattice Boltzmann methods
Sterling, J.D.; Chen, Shiyi
1996-01-01
The lattice Boltzmann equation describes the evolution of the velocity distribution function on a lattice in a manner that macroscopic fluid dynamical behavior is recovered. Although the equation is a derivative of lattice gas automata, it may be interpreted as a Lagrangian finite-difference method for the numerical simulation of the discrete-velocity Boltzmann equation that makes use of a BGK collision operator. As a result, it is not surprising that numericaI instability of lattice Boltzmann methods have been frequently encountered by researchers. We present an analysis of the stability of perturbations of the particle populations linearized about equilibrium values corresponding to a constant-density uniform mean flow. The linear stability depends on the following parameters: the distribution of the mass at a site between the different discrete speeds, the BGK relaxation time, the mean velocity, and the wave-number of the perturbations. This parameter space is too large to compute the complete stability characteristics. We report some stability results for a subset of the parameter space for a 7-velocity hexagonal lattice, a 9-velocity square lattice, and a 15-velocity cubic lattice. Results common to all three lattices are (1) the BGK relaxation time {tau} must be greater than 1/2 corresponding to positive shear viscosity, (2) there exists a maximum stable mean velocity for fixed values of theother parameters, and (3) as {tau} is increased from 1/2 the maximum stable velocity increases monotonically until some fixed velocity is reached which does not change for larger {tau}.
Lattice and Phase Diagram in QCD
Lombardo, Maria Paola
2008-10-13
Model calculations have produced a number of very interesting expectations for the QCD Phase Diagram, and the task of a lattice calculations is to put these studies on a quantitative grounds. I will give an overview of the current status of the lattice analysis of the QCD phase diagram, from the quantitative results of mature calculations at zero and small baryochemical potential, to the exploratory studies of the colder, denser phase.
Building the RHIC tracking lattice model
Luo, Y.; Fischer, W.; Tepikian, S.
2010-01-27
In this note we outline the procedure to build a realistic lattice model for the RHIC beam-beam tracking simulation. We will install multipole field errors in the arc main dipoles, arc main quadrupols and interaction region magnets (DX, D0, and triplets) and introduce a residual closed orbit, tune ripples, and physical apertures in the tracking lattice model. Nonlinearities such as local IR multipoles, second order chromaticies and third order resonance driving terms are also corrected before tracking.
Generalized Parton Distributions from Lattice QCD
Orginos, Konstantinos
2007-10-01
I review recent results on moments of Generalized Parton Distribution functions (GPDs) from Lattice QCD. In particular, I discuss the methodology of lattice calculations, and how various systematic errors arising in these calculations are controlled. I conclude with an overview of the roadmap towards precision non-perturbative determination of moments of GPDs, and discuss the potential impact to the extraction of GPDs form experiment.
The optical potential on the lattice
Agadjanov, Dimitri; Doring, Michael; Mai, Maxim; MeiBner, Ulf -G.; Rusetsky, Akaki
2016-06-08
The extraction of hadron-hadron scattering parameters from lattice data by using the Luscher approach becomes increasingly complicated in the presence of inelastic channels. We propose a method for the direct extraction of the complex hadron-hadron optical potential on the lattice, which does not require the use of the multi-channel Luscher formalism. Furthermore, this method is applicable without modifications if some inelastic channels contain three or more particles.
Lattice vibrations in lead bromide and chloride
NASA Astrophysics Data System (ADS)
Carabatos-Nédelec, C.; Bréhat, F.; Wyncke, B.
Lead bromide and lead chloride lattice dynamics studies by polarized IR reflectivity and Raman scattering are reported at room temperature and at 10 K. Reflectivity spectra from 20 to 300 cm -1 have been fitted with a model of the factorized form of the dielectric function. The lattice modes frequencies, damping factors and oscillators strengths are given, as well as the effective charges of the polar modes. The study concludes the ionic character of the compounds.
Current and lattice matched tandem solar cell
Olson, Jerry M.
1987-01-01
A multijunction (cascade) tandem photovoltaic solar cell device is fabricated of a Ga.sub.x In.sub.1-x P (0.505.ltoreq.X.ltoreq.0.515) top cell semiconductor lattice matched to a GaAs bottom cell semiconductor at a low-resistance heterojunction, preferably a p+/n+ heterojunction between the cells. The top and bottom cells are both lattice matched and current matched for high efficiency solar radiation conversion to electrical energy.
Vague Congruences and Quotient Lattice Implication Algebras
Qin, Xiaoyan; Xu, Yang
2014-01-01
The aim of this paper is to further develop the congruence theory on lattice implication algebras. Firstly, we introduce the notions of vague similarity relations based on vague relations and vague congruence relations. Secondly, the equivalent characterizations of vague congruence relations are investigated. Thirdly, the relation between the set of vague filters and the set of vague congruences is studied. Finally, we construct a new lattice implication algebra induced by a vague congruence, and the homomorphism theorem is given. PMID:25133207
Plasmonic lattice solitons in metallic nanowire materials
NASA Astrophysics Data System (ADS)
Swami, O. P.; Kumar, Vijendra; Nagar, A. K.
2016-05-01
In this paper, we demonstrate theoretically that the plasmonic lattice solitons (PLSs) are formed in array of metallic nanowires embedded in Kerr-type material. The strong nonlinearity at metal surface, combined with the tight confinement of the guiding modes of the metallic nanowires, provide the main physical mechanism for balancing the creation of plasmonic lattice solitons and wave diffraction. We show that the PLSs are satisfied in a verity of plasmonic systems, which have important applications in nanophotonics and subwavelength optics.
Lattice Boltzmann approach for complex nonequilibrium flows.
Montessori, A; Prestininzi, P; La Rocca, M; Succi, S
2015-10-01
We present a lattice Boltzmann realization of Grad's extended hydrodynamic approach to nonequilibrium flows. This is achieved by using higher-order isotropic lattices coupled with a higher-order regularization procedure. The method is assessed for flow across parallel plates and three-dimensional flows in porous media, showing excellent agreement of the mass flow with analytical and numerical solutions of the Boltzmann equation across the full range of Knudsen numbers, from the hydrodynamic regime to ballistic motion. PMID:26565365
New directions for quantum lattice gases
NASA Astrophysics Data System (ADS)
Love, Peter
2010-03-01
Quantum Lattice Gas Automata are an extension of classical Lattice Gas Automata with the added constraints of linearity and unitary evolution. They were defined in the late 1990s by Meyer, and Boghosian and Taylor. We present a unified version of these models and study them from the point of view of the quantum simulation of problems of quantum dynamics of practical interest including chemical reactive scattering.
Lattice QCD and the Jefferson Laboratory Program
Jozef Dudek, Robert Edwards, David Richards, Konstantinos Orginos
2011-06-01
Lattice gauge theory provides our only means of performing \\textit{ab initio} calculations in the non-perturbative regime. It has thus become an increasing important component of the Jefferson Laboratory physics program. In this paper, we describe the contributions of lattice QCD to our understanding of hadronic and nuclear physics, focusing on the structure of hadrons, the calculation of the spectrum and properties of resonances, and finally on deriving an understanding of the QCD origin of nuclear forces.
Topological phases: An expedition off lattice
Freedman, Michael H.; Gamper, Lukas; Gils, Charlotte; Isakov, Sergei V.; Trebst, Simon; Troyer, Matthias
2011-08-15
Highlights: > Models of topological phases where the lattice topology is a dynamical variable. > We discuss off-lattice hazards that destroy topological protection. > The Cheeger constant yields upper bound to the energy of excited states. > Baby universes meet condensed matter physics. > We study the graph Laplacian of loop gases and string nets on fluctuating lattices. - Abstract: Motivated by the goal to give the simplest possible microscopic foundation for a broad class of topological phases, we study quantum mechanical lattice models where the topology of the lattice is one of the dynamical variables. However, a fluctuating geometry can remove the separation between the system size and the range of local interactions, which is important for topological protection and ultimately the stability of a topological phase. In particular, it can open the door to a pathology, which has been studied in the context of quantum gravity and goes by the name of 'baby universe', here we discuss three distinct approaches to suppressing these pathological fluctuations. We complement this discussion by applying Cheeger's theory relating the geometry of manifolds to their vibrational modes to study the spectra of Hamiltonians. In particular, we present a detailed study of the statistical properties of loop gas and string net models on fluctuating lattices, both analytically and numerically.
Excitations of quantum gases in optical lattices
NASA Astrophysics Data System (ADS)
Yesilada, Emek
This thesis describes experiments that studied the excitations of an ultra-cold atomic Rb gas in an optical lattice using Bragg spectroscopy. A Bose-Einstein condensate (BEC) of 87Rb was formed in a cloverleaf trap. An optical lattice of cubic symmetry, formed by the interference of six laser beams, was superimposed on the Rb BEC and turned on adiabatically. Such a system is well described by the Bose-Hubbard model, which predicts a quantum phase transition from a superfluid to a Mott insulator state at a critical lattice depth. In the first experiment, we studied the superfluid regime. The superfluid admits sound waves as phonon excitations. In two photon Bragg spectroscopy two laser beams intersecting at angle on the condensate create such excitations. The excitation spectrum of BEC was measured in a three dimensional optical lattice as a function of lattice strength. In the second experiment we studied the excitation spectrum of the Mott insulator. The lowest energy excitations in such a system are particle-hole excitations. These correspond to the hopping of atoms from one lattice site to another. The insulating phase is characterized by a gap in the excitation spectrum and we measured this particle-hole gap by Bragg spectroscopy. The precise nature of our measurement allowed us to study the opening of the excitation gap that has previously eluded experimental verification.
Lattice calculation of nonleptonic charm decays
Simone, J.N.
1991-11-01
The decays of charmed mesons into two body nonleptonic final states are investigated. Weak interaction amplitudes of interest in these decays are extracted from lattice four-point correlation functions using a effective weak Hamiltonian including effects to order G{sub f} in the weak interactions yet containing effects to all orders in the strong interactions. The lattice calculation allows a quantitative examination of non-spectator processes in charm decays helping to elucidate the role of effects such as color coherence, final state interactions and the importance of the so called weak annihilation process. For D {yields} K{pi}, we find that the non-spectator weak annihilation diagram is not small, and we interpret this as evidence for large final state interactions. Moreover, there is indications of a resonance in the isospin {1/2} channel to which the weak annihilation process contributes exclusively. Findings from the lattice calculation are compared to results from the continuum vacuum saturation approximation and amplitudes are examined within the framework of the 1/N expansion. Factorization and the vacuum saturation approximation are tested for lattice amplitudes by comparing amplitudes extracted from lattice four-point functions with the same amplitude extracted from products of two-point and three-point lattice correlation functions arising out of factorization and vacuum saturation.
Some Poisson structures and Lax equations associated with the Toeplitz lattice and the Schur lattice
NASA Astrophysics Data System (ADS)
Lemarie, Caroline
2016-01-01
The Toeplitz lattice is a Hamiltonian system whose Poisson structure is known. In this paper, we unveil the origins of this Poisson structure and derive from it the associated Lax equations for this lattice. We first construct a Poisson subvariety H n of GL n (C), which we view as a real or complex Poisson-Lie group whose Poisson structure comes from a quadratic R-bracket on gl n (C) for a fixed R-matrix. The existence of Hamiltonians, associated to the Toeplitz lattice for the Poisson structure on H n , combined with the properties of the quadratic R-bracket allow us to give explicit formulas for the Lax equation. Then we derive from it the integrability in the sense of Liouville of the Toeplitz lattice. When we view the lattice as being defined over R, we can construct a Poisson subvariety H n τ of U n which is itself a Poisson-Dirac subvariety of GL n R (C). We then construct a Hamiltonian for the Poisson structure induced on H n τ , corresponding to another system which derives from the Toeplitz lattice the modified Schur lattice. Thanks to the properties of Poisson-Dirac subvarieties, we give an explicit Lax equation for the new system and derive from it a Lax equation for the Schur lattice. We also deduce the integrability in the sense of Liouville of the modified Schur lattice.
He, Xiaoyi; Lou, Li-Shi Lou, Li-Shi
1997-12-01
In this paper, the lattice Boltzmann equation is directly derived from the Boltzmann equation. It is shown that the lattice Boltzmann equation is a special discretized form of the Boltzmann equation. Various approximations for the discretization of the Boltzmann equation in both time and phase space are discussed in detail. A general procedure to derive the lattice Boltzmann model from the continuous Boltzmann equation is demonstrated explicitly. The lattice Boltzmann models derived include the two-dimensional 6-bit, 7-bit, and 9-bit, and three-dimensional 27-bit models. {copyright} {ital 1997} {ital The American Physical Society}
Spin-Lattice-Coupled Order in Heisenberg Antiferromagnets on the Pyrochlore Lattice
NASA Astrophysics Data System (ADS)
Aoyama, Kazushi; Kawamura, Hikaru
2016-06-01
Effects of local lattice distortions on the spin ordering are investigated for the antiferromagnetic classical Heisenberg model on the pyrochlore lattice. It is found by Monte Carlo simulations that the spin-lattice coupling (SLC) originating from site phonons induces a first-order transition into two different types of collinear magnetic ordered states. The state realized at the stronger SLC is cubic symmetric characterized by the magnetic (1/2 ,1/2 ,1/2 ) Bragg peaks, while that at the weaker SLC is tetragonal symmetric characterized by the (1,1,0) ones, each accompanied by the commensurate local lattice distortions. Experimental implications to chromium spinels are discussed.
Phase transitions in cooperative coinfections: Simulation results for networks and lattices
NASA Astrophysics Data System (ADS)
Grassberger, Peter; Chen, Li; Ghanbarnejad, Fakhteh; Cai, Weiran
2016-04-01
We study the spreading of two mutually cooperative diseases on different network topologies, and with two microscopic realizations, both of which are stochastic versions of a susceptible-infected-removed type model studied by us recently in mean field approximation. There it had been found that cooperativity can lead to first order transitions from spreading to extinction. However, due to the rapid mixing implied by the mean field assumption, first order transitions required nonzero initial densities of sick individuals. For the stochastic model studied here the results depend strongly on the underlying network. First order transitions are found when there are few short but many long loops: (i) No first order transitions exist on trees and on 2-d lattices with local contacts. (ii) They do exist on Erdős-Rényi (ER) networks, on d -dimensional lattices with d ≥4 , and on 2-d lattices with sufficiently long-ranged contacts. (iii) On 3-d lattices with local contacts the results depend on the microscopic details of the implementation. (iv) While single infected seeds can always lead to infinite epidemics on regular lattices, on ER networks one sometimes needs finite initial densities of infected nodes. (v) In all cases the first order transitions are actually "hybrid"; i.e., they display also power law scaling usually associated with second order transitions. On regular lattices, our model can also be interpreted as the growth of an interface due to cooperative attachment of two species of particles. Critically pinned interfaces in this model seem to be in different universality classes than standard critically pinned interfaces in models with forbidden overhangs. Finally, the detailed results mentioned above hold only when both diseases propagate along the same network of links. If they use different links, results can be rather different in detail, but are similar overall.
Smidt, Joseph; Whalen, Daniel J.; Wiggins, Brandon K.; Even, Wesley; Fryer, Chris L.; Johnson, Jarrett L.
2014-12-20
Population III supernovae have been of growing interest of late for their potential to directly probe the properties of the first stars, particularly the most energetic events that are visible near the edge of the observable universe. Until now, hypernovae, the unusually energetic Type Ib/c supernovae that are sometimes associated with gamma-ray bursts, have been overlooked as cosmic beacons at the highest redshifts. In this, the latest of a series of studies on Population III supernovae, we present numerical simulations of 25-50 M {sub ☉} hypernovae and their light curves done with the Los Alamos RAGE and SPECTRUM codes. We find that they will be visible at z = 10-15 to the James Webb Space Telescope and z = 4-5 to the Wide-Field Infrared Survey Telescope, tracing star formation rates in the first galaxies and at the end of cosmological reionization. If, however, the hypernova crashes into a dense shell ejected by its progenitor, it is expected that a superluminous event will occur that may be seen at z ∼ 20 in the first generation of stars.
Strong dynamics and lattice gauge theory
NASA Astrophysics Data System (ADS)
Schaich, David
In this dissertation I use lattice gauge theory to study models of electroweak symmetry breaking that involve new strong dynamics. Electroweak symmetry breaking (EWSB) is the process by which elementary particles acquire mass. First proposed in the 1960s, this process has been clearly established by experiments, and can now be considered a law of nature. However, the physics underlying EWSB is still unknown, and understanding it remains a central challenge in particle physics today. A natural possibility is that EWSB is driven by the dynamics of some new, strongly-interacting force. Strong interactions invalidate the standard analytical approach of perturbation theory, making these models difficult to study. Lattice gauge theory is the premier method for obtaining quantitatively-reliable, nonperturbative predictions from strongly-interacting theories. In this approach, we replace spacetime by a regular, finite grid of discrete sites connected by links. The fields and interactions described by the theory are likewise discretized, and defined on the lattice so that we recover the original theory in continuous spacetime on an infinitely large lattice with sites infinitesimally close together. The finite number of degrees of freedom in the discretized system lets us simulate the lattice theory using high-performance computing. Lattice gauge theory has long been applied to quantum chromodynamics, the theory of strong nuclear interactions. Using lattice gauge theory to study dynamical EWSB, as I do in this dissertation, is a new and exciting application of these methods. Of particular interest is non-perturbative lattice calculation of the electroweak S parameter. Experimentally S ≈ -0.15(10), which tightly constrains dynamical EWSB. On the lattice, I extract S from the momentum-dependence of vector and axial-vector current correlators. I created and applied computer programs to calculate these correlators and analyze them to determine S. I also calculated the masses
Titanium-silicon carbide composite lattice structures
NASA Astrophysics Data System (ADS)
Moongkhamklang, Pimsiree
Sandwich panel structures with stiff, strong face sheets and lightweight cellular cores are widely used for weight sensitive, bending dominated loading applications. The flexural stiffness and strength of a sandwich panel is determined by the stiffness, strength, thickness, and separation of the face sheets, and by the compressive and shear stiffness and strength of the cellular core. Panel performance can be therefore optimized using cores with high specific stiffness and strength. The specific stiffness and strength of all cellular materials depends upon the specific elastic modulus and strength of the material used to make the structure. The stiffest and strongest cores for ambient temperature applications utilize carbon fiber reinforced polymer (CFRP) honeycombs and lattice structures. Few options exist for lightweight sandwich panels intended for high temperature uses. High temperature alloys such as Ti-6A1-4V can be applied to SiC monofilaments to create very high specific modulus and strength fibers. These are interesting candidates for the cores of elevated temperature sandwich structures such as the skins of hypersonic vehicles. This dissertation explores the potential of sandwich panel concepts that utilize millimeter scale titanium matrix composite (TMC) lattice structures. A method has been developed for fabricating millimeter cell size cellular lattice structures with the square or diamond collinear truss topologies from 240 mum diameter Ti-6A1-4V coated SiC monofilaments (TMC monofilaments). Lattices with relative densities in the range 10% to 20% were manufactured and tested in compression and shear. Given the very high compressive strength of the TMC monofilaments, the compressive strengths of both the square and diamond lattices were dominated by elastic buckling of the constituent struts. However, under shear loading, some of the constituent struts of the lattices are subjected to tensile stresses and failure is then set by tensile failure of the
Quantum magnetism on kagome lattice
NASA Astrophysics Data System (ADS)
Hao, Zhihao
The spin 1/2 Heisenberg antiferromagnet on kagome (a planar lattice of corner sharing triangles) is one of the most celebrated models of a strongly correlated system. Despite intensive studies, the physics of its ground state and excitations remains unsettled. Recently, researchers successfully synthesized and characterized several new materials described by this model. It is hoped that the longstanding problem can be finally resolved through combined efforts of experimentalists, material scientists and theorists. In this thesis, we present a physical picture of the low energy physics of kagome. We demonstrate that there are N/3 fermionic particles on a kagome of N sites. The motion of these particles is strongly constrained. They are bound into small bosonic states by strong pair-wise attractions. The "antiparticle" also exists and a particle-antiparticle pair can be created at energy cost 0.218J. Low energy spin 1 excitations correspond to breaking a bound state into two free particles at energy cost 0.06J. This is the physical mechanism of the kagome spin gap. Our physical picture finds several applications. The dynamical structure factor of pair-breaking processes on kagome is computed. We assume the bound states are independent thanks to their small sizes. The result agrees well with the recent inelastic neutron scattering measurement conducted on herbertsmithite, a kagome antiferromagnet. In the second application, we study the effect of Dzyaloshinskii-Moriya (DM) interaction. DM interaction is important for low energy physics on kagome since the ground state of the dominate exchange interaction is highly degenerated. Through analytical and numerical arguments, it is determined that the vacuum become unstable to creation of particle-antiparticle pairs at critical strength D of DM interaction on the sawtooth chain, a chain of corner sharing triangles. We speculate that the mechanism is behind the numerically observed quantum phase transition at finite D on
The Spectrum and Laplacian Spectrum of the Dice Lattice
NASA Astrophysics Data System (ADS)
Li, Shuli; Yan, Weigen; Tian, Tao
2016-05-01
The dice lattice is the dual lattice of kagomé lattice. Many physical properties on the dice lattice have been studied by physicists, such as Ising model, Glassy dynamics of Josephson arrays, and Lattice Green's function. In this paper, we derive the spectrum and Laplacian spectrum of the dice lattice with toroidal boundary condition. In addition, we apply our results to obtain the formulae of the number of spanning trees, the Kirchhoff index, and the energy of the dice lattice with toroidal boundary condition.
The Spectrum and Laplacian Spectrum of the Dice Lattice
NASA Astrophysics Data System (ADS)
Li, Shuli; Yan, Weigen; Tian, Tao
2016-07-01
The dice lattice is the dual lattice of kagomé lattice. Many physical properties on the dice lattice have been studied by physicists, such as Ising model, Glassy dynamics of Josephson arrays, and Lattice Green's function. In this paper, we derive the spectrum and Laplacian spectrum of the dice lattice with toroidal boundary condition. In addition, we apply our results to obtain the formulae of the number of spanning trees, the Kirchhoff index, and the energy of the dice lattice with toroidal boundary condition.
Nuclear data uncertainty propagation in a lattice physics code using stochastic sampling
Wieselquist, W.; Vasiliev, A.; Ferroukhi, H.
2012-07-01
A methodology is presented for 'black box' nuclear data uncertainty propagation in a lattice physics code using stochastic sampling. The methodology has 4 components: i) processing nuclear data variance/covariance matrices including converting the native group structure to a group structure 'compatible' with the lattice physics code, ii) generating (relative) random samples of nuclear data, iii) perturbing the lattice physics code nuclear data according to the random samples, and iv) analyzing the distribution of outputs to estimate the uncertainty. The scheme is described as implemented at PSI, in a modified version of the lattice physics code CASMO-5M, including all relevant practical details. Uncertainty results are presented for a BWR pin-cell at hot zero power conditions and a PWR assembly at hot full power conditions with depletion. Results are presented for uncertainties in eigenvalue, 1-group microscopic cross sections, 2-group macroscopic cross sections, and isotopics. Interesting behavior is observed with burnup, including a minimum uncertainty due to the presence of fertile U-238 and a global effect described as 'synergy', observed when comparing the uncertainty resulting from simultaneous and one-at-a-time variations of nuclear data. (authors)
Holographic Fermi liquids in a spontaneously generated lattice
NASA Astrophysics Data System (ADS)
Alsup, James; Papantonopoulos, Eleftherios; Siopsis, George; Yeter, Kubra
2016-05-01
We discuss fermions in a spontaneously generated holographic lattice background. The lattice structure at the boundary is generated by introducing a higher-derivative interaction term between a U (1 ) gauge field and a scalar field. We solve the equations of motion below the critical temperature at which the lattice forms and analyze the change in the Fermi surface due to the lattice. The fermion band structure is found to exhibit a gap due to lattice effects.
Electrical properties of dislocations in III-Nitrides
Cavalcoli, D.; Minj, A.; Pandey, S.; Cavallini, A.
2014-02-21
Research on GaN, AlN, InN (III-N) and their alloys is achieving new heights due their high potential applications in photonics and electronics. III-N semiconductors are mostly grown epitaxially on sapphire, and due to the large lattice mismatch and the differences in the thermal expansion coefficients, the structures usually contain many threading dislocations (TDs). While their structural properties have been widely investigated, their electrical characteristics and their role in the transport properties of the devices are still debated. In the present contribution we will show conductive AFM studies of TDs in GaN and Al/In GaN ternary alloys to evidence the role of strain, different surface polarity and composition on their electrical properties. Local I-V curves measured at TDs allowed us to clarify their role in the macroscopic electrical properties (leakage current, mobilities) of III-N based devices. Samples obtained by different growers (AIXTRON, III-V Lab) were studied. The comparison between the results obtained in the different alloys allowed us to understand the role of In and Al on the TDs electrical properties.
Electrical properties of dislocations in III-Nitrides
NASA Astrophysics Data System (ADS)
Cavalcoli, D.; Minj, A.; Pandey, S.; Cavallini, A.
2014-02-01
Research on GaN, AlN, InN (III-N) and their alloys is achieving new heights due their high potential applications in photonics and electronics. III-N semiconductors are mostly grown epitaxially on sapphire, and due to the large lattice mismatch and the differences in the thermal expansion coefficients, the structures usually contain many threading dislocations (TDs). While their structural properties have been widely investigated, their electrical characteristics and their role in the transport properties of the devices are still debated. In the present contribution we will show conductive AFM studies of TDs in GaN and Al/In GaN ternary alloys to evidence the role of strain, different surface polarity and composition on their electrical properties. Local I-V curves measured at TDs allowed us to clarify their role in the macroscopic electrical properties (leakage current, mobilities) of III-N based devices. Samples obtained by different growers (AIXTRON, III-V Lab) were studied. The comparison between the results obtained in the different alloys allowed us to understand the role of In and Al on the TDs electrical properties.
ERIC Educational Resources Information Center
Elcoro, Luis; Etxebarria, Jesus
2011-01-01
The requirement of rotational invariance for lattice potential energies is investigated. Starting from this condition, it is shown that the Cauchy relations for the elastic constants are fulfilled if the lattice potential is built from pair interactions or when the first-neighbour approximation is adopted. This is seldom recognized in widely used…
Ammonium diphosphitoindate(III)
Hamchaoui, Farida; Rebbah, Houria; Le Fur, Eric
2013-01-01
The crystal structure of the title compound, NH4[In(HPO3)2], is built up from InIII cations (site symmetry 3m.) adopting an octahedral environment and two different phosphite anions (each with site symmetry 3m.) exhibiting a triangular–pyramidal geometry. Each InO6 octahedron shares its six apices with hydrogen phosphite groups. Reciprocally, each HPO3 group shares all its O atoms with three different metal cations, leading to [In(HPO3)2]− layers which propagate in the ab plane. The ammonium cation likewise has site symmetry 3m.. In the structure, the cations are located between the [In(HPO3)2]− layers of the host framework. The sheets are held together by hydrogen bonds formed between the NH4 + cations and the O atoms of the framework. PMID:23633983
Ammonium diphosphitoindate(III).
Hamchaoui, Farida; Rebbah, Houria; Le Fur, Eric
2013-04-01
The crystal structure of the title compound, NH4[In(HPO3)2], is built up from In(III) cations (site symmetry 3m.) adopting an octa-hedral environment and two different phosphite anions (each with site symmetry 3m.) exhibiting a triangular-pyramidal geometry. Each InO6 octa-hedron shares its six apices with hydrogen phosphite groups. Reciprocally, each HPO3 group shares all its O atoms with three different metal cations, leading to [In(HPO3)2](-) layers which propagate in the ab plane. The ammonium cation likewise has site symmetry 3m.. In the structure, the cations are located between the [In(HPO3)2](-) layers of the host framework. The sheets are held together by hydrogen bonds formed between the NH4 (+) cations and the O atoms of the framework. PMID:23633983
Al-Hummayani, Fadia M.
2016-01-01
The treatment of deep anterior crossbite is technically challenging due to the difficulty of placing traditional brackets with fixed appliances. This case report represents a none traditional treatment modality to treat deep anterior crossbite in an adult pseudo class III malocclusion complicated by severely retruded, supraerupted upper and lower incisors. Treatment was carried out in 2 phases. Phase I treatment was performed by removable appliance “modified Hawley appliance with inverted labial bow,” some modifications were carried out to it to suit the presented case. Positive overbite and overjet was accomplished in one month, in this phase with minimal forces exerted on the lower incisors. Whereas, phase II treatment was performed with fixed appliances (braces) to align teeth and have proper over bite and overjet and to close posterior open bite, this phase was accomplished within 11 month. PMID:27052290
Synthetic analogues of Fe(ii)-Fe(iii) minerals containing a pentagonal 'Cairo' magnetic lattice.
Cumby, J; Bayliss, R D; Berry, F J; Greaves, C
2016-07-19
Versiliaite and apuanite are two minerals containing Fe(2+) and Fe(3+) in a low-dimensional structure exhibiting chains of edge-linked FeO6 octahedra. The chemistry of these minerals has not been fully examined because of their rarity. We demonstrate that chemical synthesis of these minerals is possible to allow measurement of their magnetic properties and a more complete description of their structural features using neutron powder diffraction. We also show that chemical manipulation is possible to provide isostructural phases with different chemical compositions. PMID:27356761
Ultracold Quantum Gases in Hexagonal Optical Lattices
NASA Astrophysics Data System (ADS)
Sengstock, Klaus
2010-03-01
Hexagonal structures occur in a vast variety of systems, ranging from honeycombs of bees in life sciences to carbon nanotubes in material sciences. The latter, in particular its unfolded two-dimensional layer -- Graphene -- has rapidly grown to one of the most discussed topics in condensed-matter physics. Not only does it show proximity to various carbon-based materials but also exceptional properties owing to its unusual energy spectrum. In quantum optics, ultracold quantum gases confined in periodic light fields have shown to be very general and versatile instruments to mimic solid state systems. However, so far nearly all experiments were performed in cubic lattice geometries only. Here we report on the first experimental realization of ultracold quantum gases in a state-dependent, two-dimensional, Graphene-like optical lattice with hexagonal symmetry. The lattice is realized via a spin-dependent optical lattice structure with alternating σ^+ and σ^- -sites and thus constitutes a so called `magnetic'-lattice with `antiferromagnetic'-structure. Atoms with different spin orientation can be loaded to specific lattice sites or -- depending on the parameters -- to the whole lattice. As a consequence e.g. superpositions of a superfluid spin component with a different spin component in the Mott-insulating phase can be realized as well as spin-dependent transport properties, disorder etc. After preparing an antiferromagnetically ordered state we e.g. measure sustainable changes of the transport properties of the atoms. This manifests in a significant reduction of the tunneling as compared to a single-component system. We attribute this observation to a partial tunneling blockade for one spin component induced by population in another spin component localized at alternating lattice sites. Within a Gutzwiller-Ansatz we calculate the phase diagrams for the mixed spin-states and find very good agreement with our experimental results. Moreover, by state-resolved recording
Perfect Actions and Operators for Lattice QCD
NASA Astrophysics Data System (ADS)
Wiese, Uwe-Jens
1996-05-01
Wilson's renormalization group implies that lattice actions located on a renormalized trajectory emanating from a fixed point represent perfect discretizations of continuum physics. With a perfect action the spectrum of a lattice theory is identical with the one of the continuum theory even at finite lattice spacing. Similarly, perfect operators yield cut-off independent matrix elements. Hence, continuum QCD can in principle be reconstructed from a lattice with finite spacing. In practice it is difficult to construct perfect actions and perfect operators explicitly. Here perturbation theory is used to derive perfect actions for quarks and gluons by performing a block renormalization group transformation directly from the continuum. The renormalized trajectory for free massive quarks is identified and a parameter in the renormalization group transformation is tuned such that for 1-d configurations the perfect action reduces to the nearest neighbor Wilson fermion action. Then the 4-d perfect action turns out to be extremely local as well, which is vital for numerical simulations. The fixed point action for free gluons is also obtained by blocking from the continuum. For 2-d configurations it reduces to the standard plaquette action, and for 4-d configurations it is still very local. With interactions between quarks and gluons switched on the perfect quark-gluon and 3-gluon vertex functions are computed analytically. In particular, a perfect clover term can be extracted from the quark-gluon vertex. The perturbatively perfect action is directly applicable to heavy quark physics. The construction of a perfect QCD action for light quarks should include nonperturbative effects, which is possible using numerical methods. Classically perfect quark and gluon fields are constructed as well. They allow to interpolate the continuum fields from the lattice data. In this way one can obtain information about space-time regions between lattice points. The classically perfect fields
Lattice-Induced Frequency Shifts in Sr Optical Lattice Clocks at the 10{sup -17} Level
Westergaard, P. G.; Lodewyck, J.; Lecallier, A.; Millo, J.; Lemonde, P.; Lorini, L.; Burt, E. A.; Zawada, M.
2011-05-27
We present a comprehensive study of the frequency shifts associated with the lattice potential in a Sr lattice clock by comparing two such clocks with a frequency stability reaching 5x10{sup -17} after a 1 h integration time. We put the first experimental upper bound on the multipolar M1 and E2 interactions, significantly smaller than the recently predicted theoretical upper limit, and give a 30-fold improved upper limit on the effect of hyperpolarizability. Finally, we report on the first observation of the vector and tensor shifts in a Sr lattice clock. Combining these measurements, we show that all known lattice related perturbations will not affect the clock accuracy down to the 10{sup -17} level, even for lattices as deep as 150 recoil energies.
Renormalization of stochastic lattice models: basic formulation.
Haselwandter, Christoph A; Vvedensky, Dimitri D
2007-10-01
We describe a general method for the multiscale analysis of stochastic lattice models. Beginning with a lattice Langevin formulation of site fluctuations, we derive stochastic partial differential equations by regularizing the transition rules of the model. Subsequent coarse graining is accomplished by calculating renormalization-group (RG) trajectories from initial conditions determined by the regularized atomistic models. The RG trajectories correspond to hierarchies of continuum equations describing lattice models over expanding length and time scales. These continuum equations retain a quantitative connection over different scales, as well as to the underlying atomistic dynamics. This provides a systematic method for the derivation of continuum equations from the transition rules of lattice models for any length and time scales. As an illustration we consider the one-dimensional (1D) Wolf-Villain (WV) model [Europhys. Lett. 13, 389 (1990)]. The RG analysis of this model, which we develop in detail, is generic and can be applied to a wide range of conservative lattice models. The RG trajectory of the 1D WV model shows a complex crossover sequence of linear and nonlinear stochastic differential equations, which is in excellent agreement with kinetic Monte Carlo simulations of this model. We conclude by discussing possible applications of the multiscale method described here to other nonequilibrium systems. PMID:17994944
Topological phases of shaken quantum Ising lattices
NASA Astrophysics Data System (ADS)
Fernández-Lorenzo, Samuel; José García-Ripoll, Juan; Porras, Diego
2016-02-01
The quantum compass model consists of a two-dimensional square spin lattice where the orientation of the spin-spin interactions depends on the spatial direction of the bonds. It has remarkable symmetry properties and the ground state shows topological degeneracy. The implementation of the quantum compass model in quantum simulation setups like ultracold atoms and trapped ions is far from trivial, since spin interactions in those systems typically are independent of the spatial direction. Ising spin interactions, on the contrary, can be induced and controlled in atomic setups with state-of-the art experimental techniques. In this work, we show how the quantum compass model on a rectangular lattice can be simulated by the use of the photon-assisted tunneling induced by periodic drivings on a quantum Ising spin model. We describe a procedure to adiabatically prepare one of the doubly degenerate ground states of this model by adiabatically ramping down a transverse magnetic field, with surprising differences depending on the parity of the lattice size. Exact diagonalizations confirm the validity of this approach for small lattices. Specific implementations of this scheme are presented with ultracold atoms in optical lattices in the Mott insulator regime, as well as with Rydberg atoms.
The galectin lattice at a glance.
Nabi, Ivan R; Shankar, Jay; Dennis, James W
2015-07-01
Galectins are a family of widely expressed β-galactoside-binding lectins in metazoans. The 15 mammalian galectins have either one or two conserved carbohydrate recognition domains (CRDs), with galectin-3 being able to pentamerize; they form complexes that crosslink glycosylated ligands to form a dynamic lattice. The galectin lattice regulates the diffusion, compartmentalization and endocytosis of plasma membrane glycoproteins and glycolipids. The galectin lattice also regulates the selection, activation and arrest of T cells, receptor kinase signaling and the functionality of membrane receptors, including the glucagon receptor, glucose and amino acid transporters, cadherins and integrins. The affinity of transmembrane glycoproteins to the galectin lattice is proportional to the number and branching of their N-glycans; with branching being mediated by Golgi N-acetylglucosaminyltransferase-branching enzymes and the supply of UDP-GlcNAc through metabolite flux through the hexosamine biosynthesis pathway. The relative affinities of glycoproteins for the galectin lattice depend on the activities of the Golgi enzymes that generate the epitopes of their ligands and, thus, provide a means to analyze biological function of lectins and of the 'glycome' more broadly. PMID:26092931
Incommensurate lattice modulations in Potassium Vanadate
NASA Astrophysics Data System (ADS)
Chakoumakos, Bryan; Banerjee, Arnab; Mark, Lumsden; Cao, Huibo; Kim, Jong-Woo; Hoffman, Christina; Wang, Xiaoping
Potassium Vanadate (K2V3O8) is an S = 1/2 2D square lattice antiferromagnet that shows spin reorientation indicating a strong coupling between the magnetism and its dielectric properties with a promise of rich physics that promises multiferroicity. These tangible physical properties are strongly tied through a spin-lattice coupling to the underlying lattice and superlattice behavior. It has a superlattice (SL) onsetting below Tc = 115 K with an approximate [3 x 3 x 2] modulation. Here we present our recent experiments at TOPAZ beamline at SNS which for the first time proves conclusively that the lattice modulations are incommensurate, with an in-plane Q of 0.315. We will also show our attempts to refine the data using JANA which requires a redefinition of the lattice, as well as the temperature and Q dependence of the superlattice modulation measured using neutrons at HFIR and synchrotron x-rays at APS. Our results are not only relevant for the ongoing search of multifunctional behavior in K2V3O8 but also generally for the superlattice modulations observed in a large family of fresnoites. Work performed at ORNL and ANL is supported by U.S. Dept. of Energy, Office of Basic Energy Sciences and Office of User Facilities Division.
Full CKM matrix with lattice QCD
Okamoto, Masataka; /Fermilab
2004-12-01
The authors show that it is now possible to fully determine the CKM matrix, for the first time, using lattice QCD. |V{sub cd}|, |V{sub cs}|, |V{sub ub}|, |V{sub cb}| and |V{sub us}| are, respectively, directly determined with the lattice results for form factors of semileptonic D {yields} {pi}lv, D {yields} Klv, B {yields} {pi}lv, B {yields} Dlv and K {yields} {pi}lv decays. The error from the quenched approximation is removed by using the MILC unquenced lattice gauge configurations, where the effect of u, d and s quarks is included. The error from the ''chiral'' extrapolation (m{sub l} {yields} m{sub ud}) is greatly reduced by using improved staggered quarks. The accuracy is comparable to that of the Particle Data Group averages. In addition, |V{sub ud}|, |V{sub ts}|, |V{sub ts}| and |V{sub td}| are determined by using unitarity of the CKM matrix and the experimental result for sin (2{beta}). In this way, they obtain all 9 CKM matrix elements, where the only theoretical input is lattice QCD. They also obtain all the Wolfenstein parameters, for the first time, using lattice QCD.
Quantum gases in trimerized kagome lattices
Damski, B.; Fehrmann, H.; Everts, H.-U.; Baranov, M.; Santos, L.; Lewenstein, M.
2005-11-15
We study low-temperature properties of atomic gases in trimerized optical kagome lattices. The laser arrangements that can be used to create these lattices are briefly described. We also present explicit results for the coupling constants of the generalized Hubbard models that can be realized in such lattices. In the case of a single-component Bose gas the existence of a Mott insulator phase with fractional numbers of particles per trimer is verified in a mean-field approach. The main emphasis of the paper is on an atomic spinless interacting Fermi gas in the trimerized kagome lattice with two fermions per site. This system is shown to be described by a quantum spin-1/2 model on the triangular lattice with couplings that depend on the bond directions. We investigate this model by means of exact diagonalization. Our key finding is that the system exhibits nonstandard properties of a quantum spin-liquid crystal: it combines planar antiferromagnetic order in the ground state with an exceptionally large number of low-energy excitations. The possibilities of experimental verification of our theoretical results are critically discussed.
Vortex lattices in theory and practice
Capmbell, Laurence J.
1988-01-01
The formal simplicity of ideal point vortex systems in two dimensions has long attracted interest in both their exact solutions and in their capacity to simulate physical processes. Attention here is focused on infinite, two-fold periodic vortex arrays, including an expression for the energy density of an arbitrary vortex lattice (i.e., an arbitrary number of vortices with arbitrary strengths in a unit cell parallelogram of arbitrary shape). For the case of two vortices per unit cell, the morphology of stable lattices can be described completely. A non-trivial physical realization of such lattices is a rotating mixture of /sup 3/He and /sup 4/He at temperatures so low that both isotopic components are superfluid. The structure of the expected lattices is quite different from the usual triangular structure. Magnetic flux lines in high-temperature superconductors show a one-parameter family of degenerate ground state of the lattice due to the anisotropy of the vortex--vortex interaction. A final topic, closely related to Josephson-junction arrays, is the case of vortices confined to a grid. That is, the vortices interact pair-wise in the usual manner but are constrained to occupy only locations on an independent periodic grid. By using vortex relaxation methods in the continuum and then imposing the grid it is possible to find low-lying states extremely rapidly compared to previous Monte Carlo calculations. 11 refs., 8 figs.
Force constants of phosphorus (III) cyanide and arsenic (III) cyanide
NASA Astrophysics Data System (ADS)
Edwards, H. G. M.; Fawcett, V.
The force constants of phosphorus (III) cyanide and arsenic (III) cyanide have been calculated using a simple valence force-field approximation with interaction constants. Several revisions are proposed to the existing vibrational assignments for the As(CN) 3 species and the vibrational assignments for P(CN) 3 are confirmed.
MBE growth technology for high quality strained III-V layers
NASA Technical Reports Server (NTRS)
Grunthaner, Frank J. (Inventor); Liu, John K. (Inventor); Hancock, Bruce R. (Inventor)
1992-01-01
III-V films are grown on large automatically perfect terraces of III-V substrates which have a different lattice constant, with temperature and Group II and V arrival rates chosen to give a Group III element stable surface. The growth is pulsed to inhibit Group III metal accumulation to low temperature, and to permit the film to relax to equilibrium. The method of the invention 1) minimizes starting step density on sample surface; 2) deposits InAs and GaAs using an interrupted growth mode (0.25 to 2 mono-layers at a time); 3) maintains the instantaneous surface stoichiometry during growth (As-stable for GaAs, In-stable for InAs); and 4) uses time-resolved RHEED to achieve aspects (1)-14 (3).
Modeling quasi-lattice with octagonal symmetry
Girzhon, V. V.; Smolyakov, O. V.; Zakharenko, M. I.
2014-11-15
We prove the possibility to use the method of modeling of a quasi-lattice with octagonal symmetry similar to that proposed earlier for the decagonal quasicrystal. The method is based on the multiplication of the groups of basis sites according to specified rules. This model is shown to be equivalent to the method of the periodic lattice projection, but is simpler because it considers merely two-dimensional site groups. The application of the proposed modeling procedure to the reciprocal lattice of octagonal quasicrystals shows a fairly good matching with the electron diffraction pattern. Similarly to the decagonal quasicrystals, the possibility of three-index labeling of the diffraction reflections is exhibited in this case. Moreover, the ascertained ratio of indices provides information on the intensity of diffraction reflections.
Spin liquids on an anisotropic kagome lattice
NASA Astrophysics Data System (ADS)
Schaffer, Robert; Hwang, Kyusung; Huh, Yejin; Kim, Yong Baek
Much recent theoretical and experimental effort has been devoted to the search for quantum spin liquids, which arise in the presence of strong frustration of magnetic interactions. Motivated by recent experiments on the vanadium oxyfluoride material DQVOF, we examine possible spin liquid phases on an anisotropic kagome lattice of S = 1 / 2 spins, in which the C6 symmetry is broken to C3. Using the projective symmetry group analysis, we determine the possible phases for both bosonic and fermionic Z2 spin liquids on this lattice. Using VMC, we study the Heisenberg model on this lattice, and show that a Z2 spin liquid emerges as the ground state in the presence of this anisotropy.
Excited state baryon spectroscopy from lattice QCD
Robert G. Edwards; Dudek, Jozef J.; Richards, David G.; Wallace, Stephen J.
2011-10-31
Here, we present a calculation of the Nucleon and Delta excited state spectrum on dynamical anisotropic clover lattices. A method for operator construction is introduced that allows for the reliable identification of the continuum spins of baryon states, overcoming the reduced symmetry of the cubic lattice. Using this method, we are able to determine a spectrum of single-particle states for spins up to and including $J = 7/2$, of both parities, the first time this has been achieved in a lattice calculation. We find a spectrum of states identifiable as admixtures of $SU(6) Ⓧ O(3)$ representations and a counting of levels that is consistent with the non-relativistic $qqq$ constituent quark model. This dense spectrum is incompatible with quark-diquark model solutions to the "missing resonance problem" and shows no signs of parity doubling of states.
Twisted complex superfluids in optical lattices
NASA Astrophysics Data System (ADS)
Jürgensen, Ole; Sengstock, Klaus; Lühmann, Dirk-Sören
2015-09-01
We show that correlated pair tunneling drives a phase transition to a twisted superfluid with a complex order parameter. This unconventional superfluid phase spontaneously breaks the time-reversal symmetry and is characterized by a twisting of the complex phase angle between adjacent lattice sites. We discuss the entire phase diagram of the extended Bose—Hubbard model for a honeycomb optical lattice showing a multitude of quantum phases including twisted superfluids, pair superfluids, supersolids and twisted supersolids. Furthermore, we show that the nearest-neighbor interactions lead to a spontaneous breaking of the inversion symmetry of the lattice and give rise to dimerized density-wave insulators, where particles are delocalized on dimers. For two components, we find twisted superfluid phases with strong correlations between the species already for surprisingly small pair-tunneling amplitudes. Interestingly, this ground state shows an infinite degeneracy ranging continuously from a supersolid to a twisted superfluid.
Lattice QCD simulations of the Zc+ channel
NASA Astrophysics Data System (ADS)
Prelovsek, Sasa; Lang, C. B.; Leskovec, Luka; Mohler, Daniel
2016-01-01
We discuss the lattice QCD simulations that search for the Zc+ with the unconventional quark content c ¯c d ¯u in the channel IG(JPC) = 1+(1+-). The major challenge is due to the two-meson states J /Ψ π , Ψ2 Sπ , Ψ1 Dπ , D D¯*, D *D¯*, ηcρ that are also inevitably present in this channel. The available lattice simulations find expected two-meson eigenstates, but no additional eigenstate as a candidate for Zc+ . This is in a striking contrast to the lattice results in the flavour non-exotic channels, where additional states are found in relation to most of the known resonances and bound states.
Mechanical Weyl Modes in Topological Maxwell Lattices
NASA Astrophysics Data System (ADS)
Rocklin, D. Zeb; Chen, Bryan Gin-ge; Falk, Martin; Vitelli, Vincenzo; Lubensky, T. C.
2016-04-01
We show that two-dimensional mechanical lattices can generically display topologically protected bulk zero-energy phonon modes at isolated points in the Brillouin zone, analogs of massless fermion modes of Weyl semimetals. We focus on deformed square lattices as the simplest Maxwell lattices, characterized by equal numbers of constraints and degrees of freedom, with this property. The Weyl points appear at the origin of the Brillouin zone along directions with vanishing sound speed and move away to the zone edge (or return to the origin) where they annihilate. Our results suggest a design strategy for topological metamaterials with bulk low-frequency acoustic modes and elastic instabilities at a particular, tunable finite wave vector.
Exploring Three Nucleon Forces in Lattice QCD
Doi, Takumi
2011-10-21
We study the three nucleon force in N{sub f} = 2 dynamical clover fermion lattice QCD, utilizing the Nambu-Bethe-Salpeter wave function of the three nucleon system. Since parity-odd two nucleon potentials are not available in lattice QCD at this moment, we develop a new formulation to extract the genuine three nucleon force which requires only the information of parity-even two nucleon potentials. In order to handle the extremely expensive calculation cost, we consider a specific three-dimensional coordinate configuration for the three nucleons. We find that the linear setup is advantageous, where nucleons are aligned linearly with equal spacings. The lattice calculation is performed with 16{sup 3}x32 configurations at {beta} = 1.95, m{sub {pi}} = 1.13 GeV generated by CP-PACS Collaboration, and the result of the three nucleon force in triton channel is presented.
Arbitrary lattice symmetries via block copolymer nanomeshes
Majewski, Pawel W.; Rahman, Atikur; Black, Charles T.; Yager, Kevin G.
2015-01-01
Self-assembly of block copolymers is a powerful motif for spontaneously forming well-defined nanostructures over macroscopic areas. Yet, the inherent energy minimization criteria of self-assembly give rise to a limited library of structures; diblock copolymers naturally form spheres on a cubic lattice, hexagonally packed cylinders and alternating lamellae. Here, we demonstrate multicomponent nanomeshes with any desired lattice symmetry. We exploit photothermal annealing to rapidly order and align block copolymer phases over macroscopic areas, combined with conversion of the self-assembled organic phase into inorganic replicas. Repeated photothermal processing independently aligns successive layers, providing full control of the size, symmetry and composition of the nanoscale unit cell. We construct a variety of symmetries, most of which are not natively formed by block copolymers, including squares, rhombuses, rectangles and triangles. In fact, we demonstrate all possible two-dimensional Bravais lattices. Finally, we elucidate the influence of nanostructure on the electrical and optical properties of nanomeshes. PMID:26100566
Coincidence lattices in the hyperbolic plane.
Rodríguez-Andrade, M A; Aragón-González, G; Aragón, J L; Gómez-Rodríguez, A
2011-01-01
The problem of coincidences of lattices in the space R(p,q), with p + q = 2, is analyzed using Clifford algebra. We show that, as in R(n), any coincidence isometry can be decomposed as a product of at most two reflections by vectors of the lattice. Bases and coincidence indices are constructed explicitly for several interesting lattices. Our procedure is metric-independent and, in particular, the hyperbolic plane is obtained when p = q = 1. Additionally, we provide a proof of the Cartan-Dieudonné theorem for R(p,q), with p + q = 2, that includes an algorithm to decompose an orthogonal transformation into a product of reflections. PMID:21173471
Nucleon Structure from Dynamical Lattice QCD
Huey-Wen Lin
2007-06-01
We present lattice QCD numerical calculations of hadronic structure functions and form factors from full-QCD lattices, with a chirally symmetric fermion action, domain-wall fermions, for the sea and valence quarks. The lattice spacing is about 0.12 fm with physical volume approximately (2 fm)3 for RBC 2-flavor ensembles and (3 fm)3 for RBC/UKQCD 2+1-flavor dynamical ones. The lightest sea quark mass is about 1/2 the strange quark mass for the former ensembles and 1/4 for the latter ones. Our calculations include: isovector vector- and axial-charge form factors and the first few moments of the polarized and unpolarized structure functions of the nucleon. Nonperturbative renormalization in RI/MOM scheme is applied.
Nucleon Structure from Dynamical Lattice QCD
Lin, H.-W.
2007-06-13
We present lattice QCD numerical calculations of hadronic structure functions and form factors from full-QCD lattices, with a chirally symmetric fermion action, domain-wall fermions, for the sea and valence quarks. The lattice spacing is about 0.12 fm with physical volume approximately (2 fm)3 for RBC 2-flavor ensembles and (3 fm)3 for RBC/UKQCD 2+1-flavor dynamical ones. The lightest sea quark mass is about 1/2 the strange quark mass for the former ensembles and 1/4 for the latter ones. Our calculations include: isovector vector- and axial-charge form factors and the first few moments of the polarized and unpolarized structure functions of the nucleon. Nonperturbative renormalization in RI/MOM scheme is applied.
Pattern Recognition of Adsorbing HP Lattice Proteins
NASA Astrophysics Data System (ADS)
Wilson, Matthew S.; Shi, Guangjie; Wüst, Thomas; Landau, David P.; Schmid, Friederike
2015-03-01
Protein adsorption is relevant in fields ranging from medicine to industry, and the qualitative behavior exhibited by course-grained models could shed insight for further research in such fields. Our study on the selective adsorption of lattice proteins utilizes the Wang-Landau algorithm to simulate the Hydrophobic-Polar (H-P) model with an efficient set of Monte Carlo moves. Each substrate is modeled as a square pattern of 9 lattice sites which attract either H or P monomers, and are located on an otherwise neutral surface. The fully enumerated set of 102 unique surfaces is simulated with each protein sequence. A collection of 27-monomer sequences is used- each of which is non-degenerate and protein-like. Thermodynamic quantities such as the specific heat and free energy are calculated from the density of states, and are used to investigate the adsorption of lattice proteins on patterned substrates. Research supported by NSF.
Classical antiferromagnet on a hyperkagome lattice.
Hopkinson, John M; Isakov, Sergei V; Kee, Hae-Young; Kim, Yong Baek
2007-07-20
Motivated by recent experiments on Na4Ir3O8 [Y. Okamoto, M. Nohara, H. Aruga-Katori, and H. Takagi, arXiv:0705.2821 (unpublished)], we study the classical antiferromagnet on a frustrated three-dimensional lattice obtained by selectively removing one of four sites in each tetrahedron of the pyrochlore lattice. This "hyperkagome" lattice consists of corner-sharing triangles. We present the results of large-N mean field theory and Monte Carlo computations on O(N) classical spin models. It is found that the classical ground states are highly degenerate. Nonetheless a nematic order emerges at low temperatures in the Heisenberg model (N=3) via "order by disorder," representing the dominance of coplanar spin configurations. Implications for ongoing experiments are discussed. PMID:17678320
Spectroscopy of charmed baryons from lattice QCD
Padmanath, M.; Edwards, Robert G.; Mathur, Nilmani; Peardon, Michael
2015-01-01
We present the ground and excited state spectra of singly, doubly and triply charmed baryons by using dynamical lattice QCD. A large set of baryonic operators that respect the symmetries of the lattice and are obtained after subduction from their continuum analogues are utilized. Using novel computational techniques correlation functions of these operators are generated and the variational method is exploited to extract excited states. The lattice spectra that we obtain have baryonic states with well-defined total spins up to 7/2 and the low lying states remarkably resemble the expectations of quantum numbers from SU(6) x O(3) symmetry. Various energy splittings between the extracted states, including splittings due to hyperfine as well as spin-orbit coupling, are considered and those are also compared against similar energy splittings at other quark masses.
Irregular lattice model for quasistatic crack propagation
NASA Astrophysics Data System (ADS)
Bolander, J. E.; Sukumar, N.
2005-03-01
An irregular lattice model is proposed for simulating quasistatic fracture in softening materials. Lattice elements are defined on the edges of a Delaunay tessellation of the medium. The dual (Voronoi) tessellation is used to scale the elemental stiffness terms in a manner that renders the lattice elastically homogeneous. This property enables the accurate modeling of heterogeneity, as demonstrated through the elastic stress analyses of fiber composites. A cohesive description of fracture is used to model crack initiation and propagation. Numerical simulations, which demonstrate energy-conserving and grid-insensitive descriptions of cracking, are presented. The model provides a framework for the failure analysis of quasibrittle materials and fiber-reinforced brittle-matrix composites.
Josephson vortex lattice in layered superconductors
Koshelev, A. E.; Dodgson, M. J. W.
2013-09-15
Many superconducting materials are composed of weakly coupled conducting layers. Such a layered structure has a very strong influence on the properties of vortex matter in a magnetic field. This review focuses on the properties of the Josephson vortex lattice generated by the magnetic field applied in the direction of the layers. The theoretical description is based on the Lawrence-Doniach model in the London limit, which takes only the phase degree of freedom of the superconducting order parameter into account. In spite of its simplicity, this model leads to an amazingly rich set of phenomena. We review in detail the structure of an isolated vortex line and various properties of the vortex lattice, in both dilute and dense limits. In particular, we extensively discuss the influence of the layered structure and thermal fluctuations on the selection of lattice configurations at different magnetic fields.
Twisted complex superfluids in optical lattices.
Jürgensen, Ole; Sengstock, Klaus; Lühmann, Dirk-Sören
2015-01-01
We show that correlated pair tunneling drives a phase transition to a twisted superfluid with a complex order parameter. This unconventional superfluid phase spontaneously breaks the time-reversal symmetry and is characterized by a twisting of the complex phase angle between adjacent lattice sites. We discuss the entire phase diagram of the extended Bose-Hubbard model for a honeycomb optical lattice showing a multitude of quantum phases including twisted superfluids, pair superfluids, supersolids and twisted supersolids. Furthermore, we show that the nearest-neighbor interactions lead to a spontaneous breaking of the inversion symmetry of the lattice and give rise to dimerized density-wave insulators, where particles are delocalized on dimers. For two components, we find twisted superfluid phases with strong correlations between the species already for surprisingly small pair-tunneling amplitudes. Interestingly, this ground state shows an infinite degeneracy ranging continuously from a supersolid to a twisted superfluid. PMID:26345721
A Robust Approach to Lattice Thermal Conductivity
NASA Astrophysics Data System (ADS)
Nielson, Weston; Fei Zhou Team; Yi Xia Team; Vidvuds Ozolins Team
2015-03-01
Thermal conductivity is a key parameter in designing high performance thermoelectric materials. A multitude of computational methods have been developed to calculate lattice thermal conductivity. Molecular dynamics (MD) based techniques, including equilibrium and non-equilibrium methods, in addition to non MD-based solutions, such as the Boltzmann Transport Equation (BTE), are all capable of calculating thermal conductivity, but each comes with different sets of limitations and difficulties. After extensive use of these different methods, we have developed a robust set of tools for obtaining high-quality lattice thermal conductivity values of crystalline solids. The crux of our method involves a novel compressive sensing (CS) based approach for efficiently calculating high quality force constants for crystalline materials. The result is a technique for building lattice dynamical models that can treat compounds with large, complex unit cells and strong anharmonicity, including those with harmonically unstable phonon modes.
Excited state baryon spectroscopy from lattice QCD
Robert G. Edwards; Dudek, Jozef J.; Richards, David G.; Wallace, Stephen J.
2011-10-31
Here, we present a calculation of the Nucleon and Delta excited state spectrum on dynamical anisotropic clover lattices. A method for operator construction is introduced that allows for the reliable identification of the continuum spins of baryon states, overcoming the reduced symmetry of the cubic lattice. Using this method, we are able to determine a spectrum of single-particle states for spins up to and including $J = 7/2$, of both parities, the first time this has been achieved in a lattice calculation. We find a spectrum of states identifiable as admixtures of $SU(6) Ⓧ O(3)$ representations and a counting ofmore » levels that is consistent with the non-relativistic $qqq$ constituent quark model. This dense spectrum is incompatible with quark-diquark model solutions to the "missing resonance problem" and shows no signs of parity doubling of states.« less
Discrete breathers in hexagonal dusty plasma lattices
Koukouloyannis, V.; Kourakis, I.
2009-08-15
The occurrence of single-site or multisite localized vibrational modes, also called discrete breathers, in two-dimensional hexagonal dusty plasma lattices is investigated. The system is described by a Klein-Gordon hexagonal lattice characterized by a negative coupling parameter epsilon in account of its inverse dispersive behavior. A theoretical analysis is performed in order to establish the possibility of existence of single as well as three-site discrete breathers in such systems. The study is complemented by a numerical investigation based on experimentally provided potential forms. This investigation shows that a dusty plasma lattice can support single-site discrete breathers, while three-site in phase breathers could exist if specific conditions, about the intergrain interaction strength, would hold. On the other hand, out of phase and vortex three-site breathers cannot be supported since they are highly unstable.
Ising antiferromagnet on the 2-uniform lattices
NASA Astrophysics Data System (ADS)
Yu, Unjong
2016-08-01
The antiferromagnetic Ising model is investigated on the twenty 2-uniform lattices using the Monte Carlo method based on the Wang-Landau algorithm and the Metropolis algorithm to study the geometric frustration effect systematically. Based on the specific heat, the residual entropy, and the Edwards-Anderson freezing order parameter, the ground states of them were determined. In addition to the long-range-ordered phase and the spin ice phase found in the Archimedean lattices, two more phases were found. The partial long-range order is long-range order with exceptional disordered sites, which give extensive residual entropy. In the partial spin ice phase, the partial freezing phenomenon appears: A majority of sites are frozen without long-range order, but the other sites are fluctuating even at zero temperature. The spin liquid ground state was not found in the 2-uniform lattices.
Excited light meson spectroscopy from lattice QCD
Christopher Thomas, Hadron Spectrum Collaboration
2012-04-01
I report on recent progress in calculating excited meson spectra using lattice QCD, emphasizing results and phenomenology. With novel techniques we can now extract extensive spectra of excited mesons with high statistical precision, including spin-four states and those with exotic quantum numbers. As well as isovector meson spectra, I will present new calculations of the spectrum of excited light isoscalar mesons, something that has up to now been a challenge for lattice QCD. I show determinations of the flavor content of these mesons, including the eta-eta' mixing angle, providing a window on annihilation dynamics in QCD. I will also discuss recent work on using lattice QCD to map out the energy-dependent phase shift in pi-pi scattering and future applications of the methodology to the study of resonances and decays.
Experimental Realization of a Quantum Pentagonal Lattice
Yamaguchi, Hironori; Okubo, Tsuyoshi; Kittaka, Shunichiro; Sakakibara, Toshiro; Araki, Koji; Iwase, Kenji; Amaya, Naoki; Ono, Toshio; Hosokoshi, Yuko
2015-01-01
Geometric frustration, in which competing interactions give rise to degenerate ground states, potentially induces various exotic quantum phenomena in magnetic materials. Minimal models comprising triangular units, such as triangular and Kagome lattices, have been investigated for decades to realize novel quantum phases, such as quantum spin liquid. A pentagon is the second-minimal elementary unit for geometric frustration. The realization of such systems is expected to provide a distinct platform for studying frustrated magnetism. Here, we present a spin-1/2 quantum pentagonal lattice in the new organic radical crystal α-2,6-Cl2-V [=α-3-(2,6-dichlorophenyl)-1,5-diphenylverdazyl]. Its unique molecular arrangement allows the formation of a partially corner-shared pentagonal lattice (PCPL). We find a clear 1/3 magnetization plateau and an anomalous change in magnetization in the vicinity of the saturation field, which originate from frustrated interactions in the PCPL. PMID:26468930
Experimental Realization of a Quantum Pentagonal Lattice.
Yamaguchi, Hironori; Okubo, Tsuyoshi; Kittaka, Shunichiro; Sakakibara, Toshiro; Araki, Koji; Iwase, Kenji; Amaya, Naoki; Ono, Toshio; Hosokoshi, Yuko
2015-01-01
Geometric frustration, in which competing interactions give rise to degenerate ground states, potentially induces various exotic quantum phenomena in magnetic materials. Minimal models comprising triangular units, such as triangular and Kagome lattices, have been investigated for decades to realize novel quantum phases, such as quantum spin liquid. A pentagon is the second-minimal elementary unit for geometric frustration. The realization of such systems is expected to provide a distinct platform for studying frustrated magnetism. Here, we present a spin-1/2 quantum pentagonal lattice in the new organic radical crystal α-2,6-Cl2-V [=α-3-(2,6-dichlorophenyl)-1,5-diphenylverdazyl]. Its unique molecular arrangement allows the formation of a partially corner-shared pentagonal lattice (PCPL). We find a clear 1/3 magnetization plateau and an anomalous change in magnetization in the vicinity of the saturation field, which originate from frustrated interactions in the PCPL. PMID:26468930
Experimental Realization of a Quantum Pentagonal Lattice
NASA Astrophysics Data System (ADS)
Yamaguchi, Hironori; Okubo, Tsuyoshi; Kittaka, Shunichiro; Sakakibara, Toshiro; Araki, Koji; Iwase, Kenji; Amaya, Naoki; Ono, Toshio; Hosokoshi, Yuko
2015-10-01
Geometric frustration, in which competing interactions give rise to degenerate ground states, potentially induces various exotic quantum phenomena in magnetic materials. Minimal models comprising triangular units, such as triangular and Kagome lattices, have been investigated for decades to realize novel quantum phases, such as quantum spin liquid. A pentagon is the second-minimal elementary unit for geometric frustration. The realization of such systems is expected to provide a distinct platform for studying frustrated magnetism. Here, we present a spin-1/2 quantum pentagonal lattice in the new organic radical crystal α-2,6-Cl2-V [=α-3-(2,6-dichlorophenyl)-1,5-diphenylverdazyl]. Its unique molecular arrangement allows the formation of a partially corner-shared pentagonal lattice (PCPL). We find a clear 1/3 magnetization plateau and an anomalous change in magnetization in the vicinity of the saturation field, which originate from frustrated interactions in the PCPL.
Maximum independent set on diluted triangular lattices.
Fay, C W; Liu, J W; Duxbury, P M
2006-05-01
Core percolation and maximum independent set on random graphs have recently been characterized using the methods of statistical physics. Here we present a statistical physics study of these problems on bond diluted triangular lattices. Core percolation critical behavior is found to be consistent with the standard percolation values, though there are strong finite size effects. A transfer matrix method is developed and applied to find accurate values of the density and degeneracy of the maximum independent set on lattices of limited width but large length. An extrapolation of these results to the infinite lattice limit yields high precision results, which are tabulated. These results are compared to results found using both vertex based and edge based local probability recursion algorithms, which have proven useful in the analysis of hard computational problems, such as the satisfiability problem. PMID:16803003
Twisted complex superfluids in optical lattices
Jürgensen, Ole; Sengstock, Klaus; Lühmann, Dirk-Sören
2015-01-01
We show that correlated pair tunneling drives a phase transition to a twisted superfluid with a complex order parameter. This unconventional superfluid phase spontaneously breaks the time-reversal symmetry and is characterized by a twisting of the complex phase angle between adjacent lattice sites. We discuss the entire phase diagram of the extended Bose—Hubbard model for a honeycomb optical lattice showing a multitude of quantum phases including twisted superfluids, pair superfluids, supersolids and twisted supersolids. Furthermore, we show that the nearest-neighbor interactions lead to a spontaneous breaking of the inversion symmetry of the lattice and give rise to dimerized density-wave insulators, where particles are delocalized on dimers. For two components, we find twisted superfluid phases with strong correlations between the species already for surprisingly small pair-tunneling amplitudes. Interestingly, this ground state shows an infinite degeneracy ranging continuously from a supersolid to a twisted superfluid. PMID:26345721
Lattice Boltzmann model for numerical relativity.
Ilseven, E; Mendoza, M
2016-02-01
In the Z4 formulation, Einstein equations are written as a set of flux conservative first-order hyperbolic equations that resemble fluid dynamics equations. Based on this formulation, we construct a lattice Boltzmann model for numerical relativity and validate it with well-established tests, also known as "apples with apples." Furthermore, we find that by increasing the relaxation time, we gain stability at the cost of losing accuracy, and by decreasing the lattice spacings while keeping a constant numerical diffusivity, the accuracy and stability of our simulations improve. Finally, in order to show the potential of our approach, a linear scaling law for parallelization with respect to number of CPU cores is demonstrated. Our model represents the first step in using lattice kinetic theory to solve gravitational problems. PMID:26986435
Exploring hyperons and hypernuclei with lattice QCD
Beane, S.R.; Bedaque, P.F.; Parreno, A.; Savage, M.J.
2003-01-01
In this work we outline a program for lattice QCD that wouldprovide a first step toward understanding the strong and weakinteractions of strange baryons. The study of hypernuclear physics hasprovided a significant amount of information regarding the structure andweak decays of light nuclei containing one or two Lambda's, and Sigma's.From a theoretical standpoint, little is known about the hyperon-nucleoninteraction, which is required input for systematic calculations ofhypernuclear structure. Furthermore, the long-standing discrepancies inthe P-wave amplitudes for nonleptonic hyperon decays remain to beunderstood, and their resolution is central to a better understanding ofthe weak decays of hypernuclei. We present a framework that utilizesLuscher's finite-volume techniques in lattice QCD to extract thescattering length and effective range for Lambda-N scattering in both QCDand partially-quenched QCD. The effective theory describing thenonleptonic decays of hyperons using isospin symmetry alone, appropriatefor lattice calculations, is constructed.
Mechanical Weyl Modes in Topological Maxwell Lattices.
Rocklin, D Zeb; Chen, Bryan Gin-Ge; Falk, Martin; Vitelli, Vincenzo; Lubensky, T C
2016-04-01
We show that two-dimensional mechanical lattices can generically display topologically protected bulk zero-energy phonon modes at isolated points in the Brillouin zone, analogs of massless fermion modes of Weyl semimetals. We focus on deformed square lattices as the simplest Maxwell lattices, characterized by equal numbers of constraints and degrees of freedom, with this property. The Weyl points appear at the origin of the Brillouin zone along directions with vanishing sound speed and move away to the zone edge (or return to the origin) where they annihilate. Our results suggest a design strategy for topological metamaterials with bulk low-frequency acoustic modes and elastic instabilities at a particular, tunable finite wave vector. PMID:27081989
Full-deautonomisation of a lattice equation
NASA Astrophysics Data System (ADS)
Willox, R.; Mase, T.; Ramani, A.; Grammaticos, B.
2016-07-01
In this letter we report on the unexpected possibility of applying the full-deautonomisation approach we recently proposed for predicting the algebraic entropy of second-order birational mappings, to discrete lattice equations. Moreover, we show, on two examples, that the full-deautonomisation technique can in fact also be successfully applied to reductions of these lattice equations to mappings with orders higher than 2. In particular, we apply this technique to a recently discovered lattice equation that has confined singularities while being nonintegrable, and we show that our approach accurately predicts this nonintegrable character. Finally, we demonstrate how our method can even be used to predict the algebraic entropy for some nonconfining higher order mappings.
Lattice Strain Defects in a Ceria Nanolayer
2016-01-01
An ultrathin two-dimensional CeO2 (ceria) phase on a Cu(110) surface has been fabricated and fully characterized by high-resolution scanning tunneling microscopy, photoelectron spectroscopy, and density functional theory. The atomic lattice structure of the ceria/Cu(110) system is revealed as a hexagonal CeO2(111)-type monolayer separated from the Cu(110) surface by a partly disordered Cu–O intercalated buffer layer. The epitaxial coupling of the two-dimensional ceria overlayer to the Cu(110)-O surface leads to a nanoscopic stripe pattern, which creates defect regions of quasi-periodic lattice distortions. The symmetry and lattice mismatch at the interface is clarified to be responsible for the topographic stripe geometry and the related anisotropic strain defect regions at the ceria surface. This ceria monolayer is in a fully oxidized and thermodynamically stable state. PMID:26988695
Optical Lattices With Quantum Gas Microscope
NASA Astrophysics Data System (ADS)
Peng, Amy Wan-Chih
In this thesis, we demonstrate how the recent achievement of single site resolution using the "Quantum Gas Microscope" can be integrated with a system of ultra-cold atoms in a two dimensional optical lattice, to facilitate the study of condensed matter Hamiltonians in the strongly interacting regime. With the combination of magnetic and optical manipulation of atoms, we show how to reproducibly generate cold two dimensional Bose Einstein Condensates of 87Rb situated at the focus of our "Quantum Gas Microscope", allowing us to utilise the high numerical aperture for both lattice generation and single atom detection. As a first demonstration of the type of study we can perform with this apparatus, we implement the Bose-Hubbard Hamiltonian and give some evidence of the superfluid to Mott insulator transition in this system, seen on the single lattice site level.
Frequency Metrology with Optical Lattice Clocks
NASA Astrophysics Data System (ADS)
Hong, Feng-Lei; Katori, Hidetoshi
2010-08-01
The precision measurement of time and frequency is of great interest for a wide range of applications, including fundamental science and technologies that support broadband communication networks and the navigation with global positioning systems (GPSs). The development of optical frequency measurement based on frequency combs has revolutionized the field of frequency metrology, especially research on optical frequency standards. The proposal and realization of the optical lattice clock have further stimulated studies in the field of optical frequency metrology. Optical carrier transfer using optical fibers has been used to disseminate optical frequencies or compare two optical clocks without degrading their stability and accuracy. In this paper, we review the state-of-the-art development of optical frequency combs, standards, and transfer techniques with emphasis on optical lattice clocks. We address recent results achieved at the University of Tokyo and the National Metrology Institute of Japan in respect of frequency metrology with Sr and Yb optical lattice clocks.
The Abelian Higgs model on Optical Lattice?
NASA Astrophysics Data System (ADS)
Meurice, Yannick; Tsai, Shan-Wen; Bazavov, Alexei; Zhang, Jin
2015-03-01
We study the Lattice Gauge Theory of the U(1)-Higgs model in 1+1 dimensions in the strongly coupled regime. We discuss the plaquette corrections to the effective theory where link variables are integrated out. We discuss matching with the second-order perturbation theory effective Hamiltonian for various Bose-Hubbard models. This correspondence can be exploited for building a lattice gauge theory simulator on optical lattices. We propose to implement the quantum rotors which appear in the Hamiltonian formulation using Bose mixtures or p-orbitals. Recent progress on magnetic effects in 2+1 dimensions will be discussed. Supported by the Army Research Office of the Department of Defense under Award Number W911NF-13-1-0119.
QED vacuum polarization on a momentum lattice
Kroeger, H.; Lafrance, R.; Marleau, L. )
1992-12-15
We study the effect of a momentum ([ital k]) lattice as a regulator of quantum field theory. An an example, we compute the vacuum polarization in noncompact (linearized) QED from [ital k]-lattice perturbation theory to one-loop order and study the continuum limit. The amplitude has a finite part plus logarithmically, linearly, and quadratically divergent terms. The amplitude violates gauge invariance (Ward identity) and Lorentz (Euclidean) invariance and is nonlocal. For example, the linear term [similar to][Lambda][vert bar][ital k][vert bar] is nonlocal. Renormalization requires nonlocal counterterms, which is not inconsistent because the original action on the [ital k] lattice already has a nonlocality. We explicitly give the counterterms, which render the amplitude Lorentz and gauge invariant to recover the standard result.
Lattice Boltzmann model for numerical relativity
NASA Astrophysics Data System (ADS)
Ilseven, E.; Mendoza, M.
2016-02-01
In the Z4 formulation, Einstein equations are written as a set of flux conservative first-order hyperbolic equations that resemble fluid dynamics equations. Based on this formulation, we construct a lattice Boltzmann model for numerical relativity and validate it with well-established tests, also known as "apples with apples." Furthermore, we find that by increasing the relaxation time, we gain stability at the cost of losing accuracy, and by decreasing the lattice spacings while keeping a constant numerical diffusivity, the accuracy and stability of our simulations improve. Finally, in order to show the potential of our approach, a linear scaling law for parallelization with respect to number of CPU cores is demonstrated. Our model represents the first step in using lattice kinetic theory to solve gravitational problems.
Relativistic heavy quark spectrum on anisotropic lattices
NASA Astrophysics Data System (ADS)
Liao, Xiaodong
We report a fully relativistic quenched calculation of the heavy quark spectrum, including both charmonium and bottomonium, using anisotropic lattice QCD. We demonstrate that a fully relativistic treatment of a heavy quark system is well-suited to address the large systematic errors in non-relativistic calculations. In addition, the anisotropic lattice formulation is a very efficient framework for calculations requiring high temporal resolutions. A detailed excited charmonium spectrum is obtained, including both the exotic hybrids (with JPC = 1-+ , 0+-, 2+-) and orbitally excited mesons (with orbital angular momentum up to 3). Using three different lattice spacings (0.197, 0.131, and 0.092 fm), we perform a continuum extrapolation of the spectrum. The lowest lying exotic hybrid 1-+ lies at 4.428(41) GeV, slightly above the D**D (S + P wave) threshold of 4.287 GeV. Another two exotic hybrids 0+- and 2 +- are determined to be 4.70(17) GeV and 4.895(88) GeV, respectively. Our finite volume analysis confirms that our lattices are large enough to accommodate all the excited states reported here. We did the first relativistic calculation of the quenched bottomonium spectrum from anisotropic lattices. Using a very fine discretization in the temporal direction we were able to go beyond the non-relativistic approximation and perform a continuum extrapolation of our results from five different lattice spacings (0.04--0.17 fm) and two anisotropies (4 and 5). We investigate several systematic errors within the quenched approximation and compare our results with those from non-relativistic simulations.
The next linear collider damping ring lattices
Wolski, Andrzej; Corlett, John N.
2001-06-20
We report on the lattice design of the Next Linear Collider (NLC) damping rings. The damping rings are required to provide low emittance electron and positron bunch trains to the NLC linacs, at a rate of 120 Hz. We present an optical design, based on a theoretical minimum emittance (TME) lattice, to produce the required normalized extracted beam emittances gex = 3 mm-mrad and gey = 0.02 mm mrad. An assessment of dynamic aperture and non-linear effects is given. The positron pre-damping ring, required to reduce the emittance of the positron beam such that it may be accepted by a main damping ring, is also described.
Experience with split transition lattices at RHIC
Montag, C.; Tepikian, S.; Blaskiewicz, M.; Brennan, J.M.
2010-05-23
During the acceleration process, heavy ion beams in RHIC cross the transition energy. When RHIC was colliding deuterons and gold ions during Run-8, lattices with different integer tunes were used for the two rings. This resulted in the two rings crossing transition at different times, which proved beneficial for the 'Yellow' ring, the RF system of which is slaved to the 'Blue' ring. For the symmetric gold-gold run in FY2010, lattices with different transition energies but equal tunes were implemented. We report the optics design concept as well as operational experience with this configuration.
Commensurability effects in holographic homogeneous lattices
NASA Astrophysics Data System (ADS)
Andrade, Tomas; Krikun, Alexander
2016-05-01
An interesting application of the gauge/gravity duality to condensed matter physics is the description of a lattice via breaking translational invariance on the gravity side. By making use of global symmetries, it is possible to do so without scarifying homogeneity of the pertinent bulk solutions, which we thus term as "homogeneous holographic lattices." Due to their technical simplicity, these configurations have received a great deal of attention in the last few years and have been shown to correctly describe momentum relaxation and hence (finite) DC conductivities.
Increasing skyrmion lattice stability: theory and experiment
NASA Astrophysics Data System (ADS)
Kruchkov, Alex; White, Jonathan; Ronnow, Henrik; Zivkovic, Ivica
Magnetic skyrmions are vortices of spins, considered to be topologically protected against perturbations, and envisaged as very possible next-generation information carriers due to their nanoscale size. In chiral ferromagnets they form a two-dimensional hexagonal array - the skyrmion lattice. A key challenge is that bulk skyrmions have been restricted so far to a tiny region in the temperature-field phase diagram. In this work we address theoretically the stability of the skyrmion lattice. We demonstrate that tuning anisotropy can lead to dramatic (20 times) enhancement of the skyrmion phase volume, which has been recently revealed in our experiment.
Building the International Lattice Data Grid
Mark G. Beckett, Paul Coddington, Bálint Joó, Chris M. Maynard, Dirk Pleiter, Osamu Tatebe, Tomoteru Yoshie
2011-06-01
We present the International Lattice Data Grid (ILDG), a loosely federated grid-of-grids for sharing data from Lattice Quantum Chromodynamics (LQCD) simulations. The ILDG comprises of metadata, file-format and web-service standards, which can be used to wrap regional data-grid interfaces, allowing seamless access to catalogues and data in a diverse set of collaborating regional grids. We discuss the technological underpinnings of the ILDG, primarily the metadata and the middleware, and offer a critique of its various aspects with the hindsight of the design work and the two years of production.
Stern-Gerlach splitters for lattice quasispin
NASA Astrophysics Data System (ADS)
Rosado, A. S.; Franco-Villafañe, J. A.; Pineda, C.; Sadurní, E.
2016-07-01
We design a Stern-Gerlach apparatus that separates quasispin components on the lattice, without the use of external fields. The effect is engineered using intrinsic parameters, such as hopping amplitudes and on-site potentials. A theoretical description of the apparatus relying on a generalized Foldy-Wouthuysen transformation beyond Dirac points is given. Our results are verified numerically by means of wave-packet evolution, including an analysis of Zitterbewegung on the lattice. The necessary tools for microwave realizations, such as complex hopping amplitudes and chiral effects, are simulated.
Soliton dynamics in modulated Bessel photonic lattices
Ruelas, Adrian; Lopez-Aguayo, Servando; Gutierrez-Vega, Julio C.
2010-12-15
We address the existence and the controlled stability of two-dimensional solitons in modulated Bessel lattices (MBL) induced by a superposition of nondiffracting Bessel beams. We show that variation of the modulation parameter of the lattice and the initial transverse momentum of the soliton significantly modify the behavior of the solitons. We find that, under suitable and well-identified conditions, solitons propagating in the MBL exhibit six regimes of transverse mobility: stationary, oscillatory, rotating, unbounded or escape, transitional, and unstable. These results report propagating solitons that can develop these dynamics of transverse motion.
Fibonacci optical lattices for tunable quantum quasicrystals
NASA Astrophysics Data System (ADS)
Singh, K.; Saha, K.; Parameswaran, S. A.; Weld, D. M.
2015-12-01
We describe a quasiperiodic optical lattice, created by a physical realization of the abstract cut-and-project construction underlying all quasicrystals. The resulting potential is a generalization of the Fibonacci tiling. Calculation of the energies and wave functions of ultracold atoms loaded into such a lattice demonstrate a multifractal energy spectrum, a singular continuous momentum-space structure, and the existence of controllable edge states. These results open the door to cold atom quantum simulation experiments in tunable or dynamic quasicrystalline potentials, including topological pumping of edge states and phasonic spectroscopy.
Lattice Boltzmann model for compressible fluids
NASA Technical Reports Server (NTRS)
Alexander, F. J.; Chen, H.; Chen, S.; Doolen, G. D.
1992-01-01
A lattice Boltzmann model is derived which simulates compressible fluids. By choosing the parameters of the equilibrium distribution appropriately, the sound speed (which may be set arbitrarily low), bulk viscosity, and kinematic viscosity can be selected. This model simulates compressible flows and can include shocks. With a proper rescaling and zero-sound speed, this model simulates Burgers's equation. The viscosity determined by a Chapman-Enskog expansion compares well with that measured form simulations. The exact solutions of Burgers's equation on the unit circle are compared to solutions of lattice Boltzmann model finding reasonable agreement.
Fast Lattice Boltzmann Solver for Relativistic Hydrodynamics
Mendoza, M.; Herrmann, H. J.; Boghosian, B. M.; Succi, S.
2010-07-02
A lattice Boltzmann formulation for relativistic fluids is presented and numerically validated through quantitative comparison with recent hydrodynamic simulations of relativistic fluids. In order to illustrate its capability to handle complex geometries, the scheme is also applied to the case of a three-dimensional relativistic shock wave, generated by a supernova explosion, impacting on a massive interstellar cloud. This formulation opens up the possibility of exporting the proven advantages of lattice Boltzmann methods, namely, computational efficiency and easy handling of complex geometries, to the context of (mildly) relativistic fluid dynamics at large, from quark-gluon plasmas up to supernovae with relativistic outflows.
New lattice action for heavy quarks
Oktay, Mehmet B.; Kronfeld, Andreas S.
2008-03-01
We extend the Fermilab method for heavy quarks to include interactions of dimension six and seven in the action. There are, in general, many new interactions, but we carry out the calculations needed to match the lattice action to continuum QCD at the tree level, finding six non-zero couplings. Using the heavy-quark theory of cutoff effects, we estimate how large the remaining discretization errors are. We find that our tree-level matching, augmented with one-loop matching of the dimension-five interactions, can bring these errors below 1%, at currently available lattice spacings.
Excited light isoscalar mesons from lattice QCD
Christopher Thomas
2011-07-01
I report a recent lattice QCD calculation of an excited spectrum of light isoscalar mesons, something that has up to now proved challenging for lattice QCD. With novel techniques we extract an extensive spectrum with high statistical precision, including spin-four states and, for the first time, light isoscalars with exotic quantum numbers. In addition, the hidden flavour content of these mesons is determined, providing a window on annihilation dynamics in QCD. I comment on future prospects including applications to the study of resonances.
Bottomonium above Deconfinement in Lattice Nonrelativistic QCD
Aarts, G.; Kim, S.; Lombardo, M. P.; Oktay, M. B.; Ryan, S. M.; Sinclair, D. K.; Skullerud, J.-I.
2011-02-11
We study the temperature dependence of bottomonium for temperatures in the range 0.4T{sub c}
Dipolar bosons on an optical lattice ring
NASA Astrophysics Data System (ADS)
Maik, Michał; Buonsante, Pierfrancesco; Vezzani, Alessandro; Zakrzewski, Jakub
2011-11-01
We consider an ultrasmall system of polarized bosons on an optical lattice with a ring topology, interacting via long-range dipole-dipole interactions. Dipoles polarized perpendicular to the plane of the ring reveal sharp transitions between different density-wave phases. As the strength of the dipolar interactions is varied, the behavior of the transitions is first-order-like. For dipoles polarized in the plane of the ring, the transitions between possible phases show pronounced sensitivity to the lattice depth. The abundance of possible configurations may be useful for quantum-information applications.
Scattering processes in lattice gauge theories
NASA Astrophysics Data System (ADS)
Alessandrini, V.; Krzywicki, A.
1980-06-01
Scattering between gauge invariant lattice excitations is studied in the framework of a 2+1 dimensional lattice theory with U(1) gauge symmetry. We put the theory in a form analogous to theories of conventional large quantum systems (spin waves in a solid, for example) and we calculate explicitly the cross section for boxiton scattering. The general strategy we have developed goes beyond the simple example of compact QED. Laboratoire associé au CNRS. Postal address: LPTHE, Bâtiment 211, Université Paris-Sud, 91405 Orsay, France.
Lattice Strain Due to an Atomic Vacancy
Li, Shidong; Sellers, Michael S.; Basaran, Cemal; Schultz, Andrew J.; Kofke, David A.
2009-01-01
Volumetric strain can be divided into two parts: strain due to bond distance change and strain due to vacancy sources and sinks. In this paper, efforts are focused on studying the atomic lattice strain due to a vacancy in an FCC metal lattice with molecular dynamics simulation (MDS). The result has been compared with that from a continuum mechanics method. It is shown that using a continuum mechanics approach yields constitutive results similar to the ones obtained based purely on molecular dynamics considerations. PMID:19582230
Interface fluctuations on a hierarchical lattice
NASA Astrophysics Data System (ADS)
Iglói, Ferenc; Szalma, Ferenc
1996-08-01
We consider interface fluctuations on a two-dimensional layered lattice where the couplings follow a hierarchical sequence. This problem is equivalent to the diffusion process of a quantum particle in the presence of a one-dimensional hierarchical potential. According to a modified Harris criterion, this type of perturbation is relevant and one expects anomalous fluctuating behavior. By transfer-matrix techniques and by an exact renormalization-group transformation we have obtained analytical results for the interface fluctuation exponents, which are discontinuous at the homogeneous lattice limit.
Strangeness of the nucleon from lattice QCD
NASA Astrophysics Data System (ADS)
Alexandrou, Constantia; Constantinou, Martha; Dinter, Simon; Drach, Vincent; Hadjiyiannakou, Kyriakos; Jansen, Karl; Koutsou, Giannis; Vaquero, Alejandro; ETM Collaboration
2015-05-01
We present a nonperturbative calculation of the strangeness of the nucleon yN within the framework of lattice QCD. This observable is known to be an important cornerstone to interpret results from direct dark matter detection experiments. We perform a lattice computation for yN with an analysis of systematic effects originating from discretization, finite size, chiral extrapolation and excited state effects leading to the value of yN=0.173 (50 ) . The rather large uncertainty of this value of yN is dominated by systematic uncertainties which we are able to quantify in this work.
DESIGN OF THE RCMS LATTICE OPTICS.
CARDONA,J.; KEWISCH,J.; PEGGS,S.
2002-06-02
THE RAPID CYCLING MEDICAL SYNCHROTRON (RCMS) IS DESIGNED TO BE A VERY LIGHT AND INEXPENSIVE ACCELERATOR. THIS IS POSSIBLE DUE TO THE SMALL BEAM SIZE THAT HAS BEEN CHOSEN EARLY DURING THE DESIGN STAGE. THIS CHOICE HAS IMPLICATIONS IN THE DESIGN OF THE LATTICE OPTICS. IN THIS PAPER, WE PRESENT AN OVERVIEW OF THE RCMS OPTICS LATTICE, THE KIND OF MAGNETS TO BE USED AND ALSO A DESCRIPTION OF A SPECIAL OPTIC MODULE THAT MATCHES THE ROTATING GANTRY WITH THE REST OF THE FIXED ACCELERATOR. TECHNIQUESDEVELOPED TO WIN ADDITIONAL SPACE BETWEEN QUADRUPOLES WITHOUT DISTRUBING BETA FUNCTIONS ARE ALSO PRESENTED.
Narrow line photoassociation in an optical lattice.
Zelevinsky, T; Boyd, M M; Ludlow, A D; Ido, T; Ye, J; Ciuryło, R; Naidon, P; Julienne, P S
2006-05-26
With ultracold 88Sr in a 1D magic wavelength optical lattice, we performed narrow-line photoassociation spectroscopy near the 1S0 - 3P1 intercombination transition. Nine least-bound vibrational molecular levels associated with the long-range 0u and 1u potential energy surfaces were measured and identified. A simple theoretical model accurately describes the level positions and treats the effects of the lattice confinement on the line shapes. The measured resonance strengths show that optical tuning of the ground state scattering length should be possible without significant atom loss. PMID:16803171
Statistical Transmutation in Floquet Driven Optical Lattices
NASA Astrophysics Data System (ADS)
Sedrakyan, Tigran A.; Galitski, Victor M.; Kamenev, Alex
2015-11-01
We show that interacting bosons in a periodically driven two dimensional (2D) optical lattice may effectively exhibit fermionic statistics. The phenomenon is similar to the celebrated Tonks-Girardeau regime in 1D. The Floquet band of a driven lattice develops the moat shape, i.e., a minimum along a closed contour in the Brillouin zone. Such degeneracy of the kinetic energy favors fermionic quasiparticles. The statistical transmutation is achieved by the Chern-Simons flux attachment similar to the fractional quantum Hall case. We show that the velocity distribution of the released bosons is a sensitive probe of the fermionic nature of their stationary Floquet state.
Statistical Transmutation in Floquet Driven Optical Lattices.
Sedrakyan, Tigran A; Galitski, Victor M; Kamenev, Alex
2015-11-01
We show that interacting bosons in a periodically driven two dimensional (2D) optical lattice may effectively exhibit fermionic statistics. The phenomenon is similar to the celebrated Tonks-Girardeau regime in 1D. The Floquet band of a driven lattice develops the moat shape, i.e., a minimum along a closed contour in the Brillouin zone. Such degeneracy of the kinetic energy favors fermionic quasiparticles. The statistical transmutation is achieved by the Chern-Simons flux attachment similar to the fractional quantum Hall case. We show that the velocity distribution of the released bosons is a sensitive probe of the fermionic nature of their stationary Floquet state. PMID:26588392
Hexagonal structure of baby Skyrmion lattices
Hen, Itay; Karliner, Marek
2008-03-01
We study the zero-temperature crystalline structure of baby Skyrmions by applying a full-field numerical minimization algorithm to baby Skyrmions placed inside different parallelogramic unit cells and imposing periodic boundary conditions. We find that within this setup, the minimal energy is obtained for the hexagonal lattice, and that in the resulting configuration the Skyrmion splits into quarter Skyrmions. In particular, we find that the energy in the hexagonal case is lower than the one obtained on the well-studied rectangular lattice, in which splitting into half Skyrmions is observed.
YANG-MILLS FIELDS AND THE LATTICE.
CREUTZ,M.
2004-05-18
The Yang-Mills theory lies at the heart of our understanding of elementary particle interactions. For the strong nuclear forces, we must understand this theory in the strong coupling regime. The primary technique for this is the lattice. While basically an ultraviolet regulator, the lattice avoids the use of a perturbative expansion. I discuss some of the historical circumstances that drove us to this approach, which has had immense success, convincingly demonstrating quark confinement and obtaining crucial properties of the strong interactions from first principles.
Compact polymers on decorated square lattices
NASA Astrophysics Data System (ADS)
Higuchi, Saburo
1999-05-01
A Hamiltonian cycle of a graph is a closed path that visits every vertex once and only once. It serves as a model of a compact polymer on a lattice. I study the number of Hamiltonian cycles, or equivalently the entropy of a compact polymer, on various lattices that are not homogeneous but with a sublattice structure. Estimates for the number are obtained by two methods. One is the saddle point approximation for a field theoretic representation. The other is the numerical diagonalization of the transfer matrix of a fully packed loop model in the zero fugacity limit. In the latter method, several scaling exponents are also obtained.
Ultracold quantum gases in optical lattices
NASA Astrophysics Data System (ADS)
Bloch, Immanuel
2005-10-01
Artificial crystals of light, consisting of hundreds of thousands of optical microtraps, are routinely created by interfering optical laser beams. These so-called optical lattices act as versatile potential landscapes to trap ultracold quantum gases of bosons and fermions. They form powerful model systems of quantum many-body systems in periodic potentials for probing nonlinear wave dynamics and strongly correlated quantum phases, building fundamental quantum gates or observing Fermi surfaces in periodic potentials. Optical lattices represent a fast-paced modern and interdisciplinary field of research.
Towards an interoperable International Lattice Datagrid
G. Beckett; P. Coddington; N. Ishii; B. Joo; D. Melkumyan; R. Ostrowski; D. Pleiter; M. Sato; J. Simone; C. Watson; S. Zhang
2007-11-01
The International Lattice Datagrid (ILDG) is a federation of several regional grids. Since most of these grids have reached production level, an increasing number of lattice scientists start to benefit from this new research infrastructure. The ILDG Middleware Working Group has the task of specifying the ILDG middleware such that interoperability among the different grids is achieved. In this paper we will present the architecture of the ILDG middleware and describe what has actually been achieved in recent years. Particular focus is given to interoperability and security issues. We will conclude with a short overview on issues which we plan to address in the near future.
On Vectorization for Lattice Based Simulations
NASA Astrophysics Data System (ADS)
Shet, Aniruddha G.; Siddharth, K.; Sorathiya, Shahajhan H.; Deshpande, Anand M.; Sherlekar, Sunil D.; Kaul, Bharat; Ansumali, Santosh
2013-12-01
We present a vector-friendly blocked computing strategy for the lattice Boltzmann method (LBM). This strategy, along with a recently developed data structure, Structure of Arrays of Structures (SoAoS), is implemented for multi-relaxation type lattice Boltzmann (LB). The proposed methodology enables optimal memory bandwidth utilization in the advection step and high compute efficiency in the collision step of LB implementation. In a dense computing environment, current performance optimization framework for LBM is able to achieve high single-core efficiency.
String breaking in four dimensional lattice QCD
Duncan, A.; Eichten, E.; Thacker, H.
2001-06-01
Virtual quark pair screening leads to breaking of the string between fundamental representation quarks in QCD. For unquenched four dimensional lattice QCD, this (so far elusive) phenomenon is studied using the recently developed truncated determinant algorithm (TDA). The dynamical configurations were generated on a 650 MHz PC. Quark eigenmodes up to 420 MeV are included exactly in these TDA studies performed at low quark mass on large coarse [but O(a{sup 2}) improved] lattices. A study of Wilson line correlators in Coulomb gauge extracted from an ensemble of 1000 two-flavor dynamical configurations reveals evidence for flattening of the string tension at distances R{approx}>1 fm.
Lattice Gas Model with Nonlocal Interactions
NASA Astrophysics Data System (ADS)
Das, Shankar P.
We analyze the nature of the hydrodynamic modes in a Lattice Gas Automata (LGA) model defined on a hexagonal lattice and having nonlocal interactions of attractive and repulsive type simultaneously. The model is similar in spirit to the liquid gas model of Appert and Zaleski [Phys. Rev. Lett. 64, 1 (1990)]. The phase diagram for the model is computed using the kinetic pressure. The dynamics is studied with a mean field type approach in the Boltzmann approximation ignoring effects of correlated collisions. We compute the transport coefficients and the speed of sound propagation. The presence of attractive interactions show increase in the transport coefficients at intermediate densities.
Title III in Special Education.
ERIC Educational Resources Information Center
The Title III Quarterly, 1972
1972-01-01
The journal on special education programs funded under Title III of the Elementary and Secondary Education Act contains articles on three projects, abstracts of other projects, a picture story on San Diego Schools' outdoor classroom for special education, and a state by state listing of all Title III special education projects. The programs…
ERIC Educational Resources Information Center
North Carolina State Dept. of Public Education, Raleigh.
SUPERSTARS III is a K-8 program designed as an enrichment opportunity for self-directed learners in mathematics. The basic purpose of SUPERSTARS III is to provide the extra challenge that self-motivated students need in mathematics and to do so in a structured, long-term program that does not impinge on the normal classroom routine or the…
ERIC Educational Resources Information Center
North Carolina State Dept. of Public Education, Raleigh.
SUPERSTARS III is a K-8 program designed as an enrichment opportunity for self-directed learners in mathematics. The basic purpose of SUPERSTARS III is to provide the extra challenge that self-motivated students need in mathematics and to do so in a structured, long-term program that does not impinge on the normal classroom routine or the…
NASA Astrophysics Data System (ADS)
Jiang, F. D.; Feng, J. Y.
2008-02-01
Using first principles calculation, we systematically investigate the electronic modification of Cu-based chalcopyrite semiconductors induced by lattice deformation and composition alchemy. It is shown that the optical band gap Eg is remarkably sensitive to the anion displacement μ, resulting from the opposite shifts of conduction band minimum and valence band maximum. Meanwhile, the dependence of structural parameters of alloyed compounds on alloy composition x is demonstrated for both cation and anion alloying. The d orbitals of group-III cations are found to be of great importance in the calculation. Abnormal changes in the optical band gap Eg induced by anion alloying are addressed.
Ternary free-energy lattice Boltzmann model with tunable surface tensions and contact angles
NASA Astrophysics Data System (ADS)
Semprebon, Ciro; Krüger, Timm; Kusumaatmaja, Halim
2016-03-01
We present a ternary free-energy lattice Boltzmann model. The distinguishing feature of our model is that we are able to analytically derive and independently vary all fluid-fluid surface tensions and the solid surface contact angles. We carry out a number of benchmark tests: (i) double emulsions and liquid lenses to validate the surface tensions, (ii) ternary fluids in contact with a square well to compare the contact angles against analytical predictions, and (iii) ternary phase separation to verify that the multicomponent fluid dynamics is accurately captured. Additionally we also describe how the model presented here can be extended to include an arbitrary number of fluid components.
Challenges in assignment of orbital populations in a high spin manganese(iii) complex.
Fitzpatrick, A J; Stepanovic, S; Müller-Bunz, H; Gruden-Pavlović, M A; García-Fernández, P; Morgan, G G
2016-04-12
Magnetic, structural and computational data of four complex salts with the same mononuclear high spin octahedral Mn(iii) complex cation are reported. The manifestation of Jahn-Teller-like distortions in the Mn(iii) cation is dependent on the nature of the charge-balancing anion, with small anions yielding a planar elongation and large anions freezing out a preferential axial elongation along one of the amine-Mn-imine directions within that same plane. Modulation of the lattice by changing the charge balancing anion results in mixing of the orbital symmetry due to vibrational perturbation. PMID:26974518
Chaos in the honeycomb optical-lattice unit cell
NASA Astrophysics Data System (ADS)
Porter, Max D.; Reichl, L. E.
2016-01-01
Natural and artificial honeycomb lattices are of great interest because the band structure of these lattices, if properly constructed, contains a Dirac point. Such lattices occur naturally in the form of graphene and carbon nanotubes. They have been created in the laboratory in the form of semiconductor 2DEGs, optical lattices, and photonic crystals. We show that, over a wide energy range, gases (of electrons, atoms, or photons) that propagate through these lattices are Lorentz gases and the corresponding classical dynamics is chaotic. Thus honeycomb lattices are also of interest for understanding eigenstate thermalization and the conductor-insulator transition due to dynamic Anderson localization.
Antiferromagnetic Spinor Condensates in a Two-Dimensional Optical Lattice.
Zhao, L; Jiang, J; Tang, T; Webb, M; Liu, Y
2015-06-01
We experimentally demonstrate that spin dynamics and the phase diagram of spinor condensates can be conveniently tuned by a two-dimensional optical lattice. Spin population oscillations and a lattice-tuned separatrix in phase space are observed in every lattice where a substantial superfluid fraction exists. In a sufficiently deep lattice, we observe a phase transition from a longitudinal polar phase to a broken-axisymmetry phase in steady states of lattice-confined spinor condensates. The steady states are found to depend sigmoidally on the lattice depth and exponentially on the magnetic field. We also introduce a phenomenological model that semiquantitatively describes our data without adjustable parameters. PMID:26196625
An optochemically organized nonlinear waveguide lattice with primitive cubic symmetry.
Ponte, Matthew R; Welch, Robert; Saravanamuttu, Kalaichelvi
2013-02-25
We describe the first example of a primitive cubic lattice assembled spontaneously from three mutually orthogonal and intersecting arrays of cylindrical, multimode waveguides. The lattice is generated in a single, room-temperature step with separate (mutually incoherent) incandescent light bulbs. To demonstrate its potential as a nonlinear photonic lattice, we generated a self-trapped lattice beam of incoherent white light. These two findings open entirely new experimental opportunities to study the behavior of spatially and temporally incoherent, polychromatic lattice solitons in 3-D Bravais lattices. PMID:23481954
Twisted 3D N=4 supersymmetric YM on deformed A{sub 3}{sup *} lattice
Saidi, El Hassan
2014-01-15
We study a class of twisted 3D N=4 supersymmetric Yang-Mills (SYM) theory on particular 3-dimensional lattice L{sub 3D} formally denoted as L{sub 3D}{sup su{sub 3}×u{sub 1}} and given by non-trivial fibration L{sub 1D}{sup u{sub 1}}×L{sub 2D}{sup su{sub 3}} with base L{sub 2D}{sup su{sub 3}}=A{sub 2}{sup *}, the weight lattice of SU(3). We first, develop the twisted 3D N=4 SYM in continuum by using superspace method where the scalar supercharge Q is manifestly exhibited. Then, we show how to engineer the 3D lattice L{sub 3D}{sup su{sub 3}×u{sub 1}} that host this theory. After that we build the lattice action S{sub latt} invariant under the following three points: (i) U(N) gauge invariance, (ii) BRST symmetry, (iii) the S{sub 3} point group symmetry of L{sub 3D}{sup su{sub 3}×u{sub 1}}. Other features such as reduction to twisted 2D supersymmetry with 8 supercharges living on L{sub 2D}≡L{sub 2D}{sup su{sub 2}×u{sub 1}}, the extension to twisted maximal 5D SYM with 16 supercharges on lattice L{sub 5D}≡L{sub 5D}{sup su{sub 4}×u{sub 1}} as well as the relation with known results are also given.
Sustainable sex ratio in lattice populations
NASA Astrophysics Data System (ADS)
Tainaka, K.; Hayashi, T.; Yoshimura, J.
2006-05-01
We present a lattice model of mating populations. Simulation is performed by two different methods: local and global interactions. Simulation results account for the reason why the observed sex ratio is nearly one half in many animals. The male-biased sex ratio, such as in human populations, is also explained.
Large Scale Commodity Clusters for Lattice QCD
A. Pochinsky; W. Akers; R. Brower; J. Chen; P. Dreher; R. Edwards; S. Gottlieb; D. Holmgren; P. Mackenzie; J. Negele; D. Richards; J. Simone; W. Watson
2002-06-01
We describe the construction of large scale clusters for lattice QCD computing being developed under the umbrella of the U.S. DoE SciDAC initiative. We discuss the study of floating point and network performance that drove the design of the cluster, and present our plans for future multi-Terascale facilities.
Ultra-Cold Atoms on Optical Lattices
ERIC Educational Resources Information Center
Ghosh, Parag
2009-01-01
The field of ultra-cold atoms, since the achievement of Bose-Einstein Condensation (Anderson et al., 1995; Davis et al., 1995; Bradley et al., 1995), have seen an immensely growing interest over the past decade. With the creation of optical lattices, new possibilities of studying some of the widely used models in condensed matter have opened up.…
A Lattice Model for Influenza Spreading
Liccardo, Antonella; Fierro, Annalisa
2013-01-01
We construct a stochastic SIR model for influenza spreading on a D-dimensional lattice, which represents the dynamic contact network of individuals. An age distributed population is placed on the lattice and moves on it. The displacement from a site to a nearest neighbor empty site, allows individuals to change the number and identities of their contacts. The dynamics on the lattice is governed by an attractive interaction between individuals belonging to the same age-class. The parameters, which regulate the pattern dynamics, are fixed fitting the data on the age-dependent daily contact numbers, furnished by the Polymod survey. A simple SIR transmission model with a nearest neighbors interaction and some very basic adaptive mobility restrictions complete the model. The model is validated against the age-distributed Italian epidemiological data for the influenza A(H1N1) during the season, with sensible predictions for the epidemiological parameters. For an appropriate topology of the lattice, we find that, whenever the accordance between the contact patterns of the model and the Polymod data is satisfactory, there is a good agreement between the numerical and the experimental epidemiological data. This result shows how rich is the information encoded in the average contact patterns of individuals, with respect to the analysis of the epidemic spreading of an infectious disease. PMID:23717512
Numerical techniques for lattice gauge theories
Creutz, M.
1981-02-06
The motivation for formulating gauge theories on a lattice is reviewed. Monte Carlo simulation techniques are then discussed for these systems. Finally, the Monte Carlo methods are combined with renormalization group analysis to give strong numerical evidence for confinement of quarks by non-Abelian gauge fields.
Experimental study of photonic crystal triangular lattices
NASA Astrophysics Data System (ADS)
Qin, Ruhu; Qin, Bo; Jin, Chongjun
1999-06-01
Triangular lattice photonic crystal behaving in the electromagnetic zones constructed from fused silica cylinders in styrofoam is fabricated. The transmission spectra of the photonic crystal with and without defects are measured. On this basis, the defect modes of photonic crystal were studied, and the potential applications of the photonic crystal are discussed.
Toward lattice QCD simulation on AP1000
NASA Astrophysics Data System (ADS)
Ohta, Shigemi
AP1000 is Fujitsu Laboratory's experimental parallel computer consisting of up to 1024 microcomputers called cells. It is found that each AP1000 cell can sustain two to three megaflops computational speed for full QCD lattice numerical simulations in IEEE 64-bit floating point format
Spin squeezing in a Rydberg lattice clock.
Gil, L I R; Mukherjee, R; Bridge, E M; Jones, M P A; Pohl, T
2014-03-14
We theoretically demonstrate a viable approach to spin squeezing in optical lattice clocks via optical dressing of one clock state to a highly excited Rydberg state, generating switchable atomic interactions. For realistic experimental parameters, these interactions are shown to generate over 10 dB of squeezing in large ensembles within a few microseconds and without degrading the subsequent clock interrogation. PMID:24679291
Radiative Transitions in Charmonium from Lattice QCD
Jozef Dudek; Robert Edwards; David Richards
2006-01-17
Radiative transitions between charmonium states offer an insight into the internal structure of heavy-quark bound states within QCD. We compute, for the first time within lattice QCD, the transition form-factors of various multipolarities between the lightest few charmonium states. In addition, we compute the experimentally unobservable, but physically interesting vector form-factors of the {eta}{sub c}, J/{psi} and {chi}{sub c0}. To this end we apply an ambitious combination of lattice techniques, computing three-point functions with heavy domain wall fermions on an anisotropic lattice within the quenched approximation. With an anisotropy {xi} = 3 at a{sub s} {approx} 0.1 fm we find a reasonable gross spectrum and a hyperfine splitting {approx}90 MeV, which compares favorably with other improved actions. In general, after extrapolation of lattice data at non-zero Q{sup 2} to the photopoint, our results agree within errors with all well measured experimental values. Furthermore, results are compared with the expectations of simple quark models where we find that many features are in agreement; beyond this we propose the possibility of constraining such models using our extracted values of physically unobservable quantities such as the J/{psi} quadrupole moment. We conclude that our methods are successful and propose to apply them to the problem of radiative transitions involving hybrid mesons, with the eventual goal of predicting hybrid meson photoproduction rates at the GlueX experiment.
Anatomy of the lattice magnetic monopoles
NASA Astrophysics Data System (ADS)
Bornyakov, V. G.; Chernodub, M. N.; Gubarev, F. V.; Polikarpov, M. I.; Suzuki, T.; Veselov, A. I.; Zakharov, V. I.
2002-06-01
We study the Abelian and non-Abelian action density near the monopole in the maximal Abelian gauge of /SU(2) lattice gauge theory. We find that the non-Abelian action density near the monopoles belonging to the percolating cluster decreases when we approach the monopole center. Our estimate of the monopole radius is Rmon~0.04 fm.
THE EARLY DAYS OF LATTICE GAUGE THEORY.
CREUTZ,M.
2003-06-09
I discuss some of the historical circumstances that drove us to use the lattice as a non-perturbative regulator. This approach has had immense success, convincingly demonstrating quark confinement and obtaining crucial properties of the strong interactions from first principles. I wrap up with some challenges for the future.
On lattice protein structure prediction revisited.
Dotu, Ivan; Cebrián, Manuel; Van Hentenryck, Pascal; Clote, Peter
2011-01-01
Protein structure prediction is regarded as a highly challenging problem both for the biology and for the computational communities. In recent years, many approaches have been developed, moving to increasingly complex lattice models and off-lattice models. This paper presents a Large Neighborhood Search (LNS) to find the native state for the Hydrophobic-Polar (HP) model on the Face-Centered Cubic (FCC) lattice or, in other words, a self-avoiding walk on the FCC lattice having a maximum number of H-H contacts. The algorithm starts with a tabu-search algorithm, whose solution is then improved by a combination of constraint programming and LNS. The flexible framework of this hybrid algorithm allows an adaptation to the Miyazawa-Jernigan contact potential, in place of the HP model, thus suggesting its potential for tertiary structure prediction. Benchmarking statistics are given for our method against the hydrophobic core threading program HPstruct, an exact method which can be viewed as complementary to our method. PMID:21358007
Recycler lattice for Project X at Fermilab
Xiao, Meiqin; Johnson, David E.; /Fermilab
2009-09-01
Project X is an intense proton source that provides beam for various physics programs. The source consists of an 8 GeV H- superconducting linac that injects into the Fermilab Recycler where H- are converted to protons. Protons are provided to the Main Injector and accelerated to desired energy (in the range 60-120 GeV) or extracted from the Recycler for the 8 GeV program. A long drift space is needed to accommodate the injection chicane with stripping foils. The Recycler is a fixed 8 GeV kinetic energy storage ring using permanent gradient magnets. A phase trombone straight section is used to control the tunes. In this paper, the existing FODO lattice in RR10 straight section being converted into doublet will be described. Due to this change, the phase trombone straight section has to be modified to bring the tunes to the nominal working point. A toy lattice of recycler ring is designed to simulate the end-shim effects of each permanent gradient magnet to add the flexibility to handle the tune shift to the lattice during the operation of 1.6E14 with KV distribution of the proton beam to give {approx}0.05 of space charge tune shift. The comparison or the combinations of the two modification ways for the Recycler ring lattice will be presented also in this paper.
Mechanical properties of lattice grid composites
NASA Astrophysics Data System (ADS)
Fan, Hualin; Fang, Daining; Jin, Fengnian
2008-08-01
An equivalent continuum method only considering the stretching deformation of struts was used to study the in-plane stiffness and strength of planar lattice grid composite materials. The initial yield equations of lattices were deduced. Initial yield surfaces were depicted separately in different 3D and 2D stress spaces. The failure envelope is a polyhedron in 3D spaces and a polygon in 2D spaces. Each plane or line of the failure envelope is corresponding to the yield or buckling of a typical bar row. For lattices with more than three bar rows, subsequent yield of the other bar row after initial yield made the lattice achieve greater limit strength. The importance of the buckling strength of the grids was strengthened while the grids were relative sparse. The integration model of the method was used to study the nonlinear mechanical properties of strain hardening grids. It was shown that the integration equation could accurately model the complete stress-strain curves of the grids within small deformations.
Extension theorems for homogenization on lattice structures
NASA Technical Reports Server (NTRS)
Miller, Robert E.
1992-01-01
When applying homogenization techniques to problems involving lattice structures, it is necessary to extend certain functions defined on a perforated domain to a simply connected domain. This paper provides general extension operators which preserve bounds on derivatives of order l. Only the special case of honeycomb structures is considered.
Lattice QCD and High Baryon Density State
Nagata, Keitaro; Nakamura, Atsushi; Motoki, Shinji; Nakagawa, Yoshiyuki; Saito, Takuya
2011-10-21
We report our recent studies on the finite density QCD obtained from lattice QCD simulation with clover-improved Wilson fermions of two flavor and RG-improved gauge action. We approach the subject from two paths, i.e., the imaginary and chemical potentials.
Marking up lattice QCD configurations and ensembles
P.Coddington; B.Joo; C.M.Maynard; D.Pleiter; T.Yoshie
2007-10-01
QCDml is an XML-based markup language designed for sharing QCD configurations and ensembles world-wide via the International Lattice Data Grid (ILDG). Based on the latest release, we present key ingredients of the QCDml in order to provide some starting points for colleagues in this community to markup valuable configurations and submit them to the ILDG.
Mechanical cloak design by direct lattice transformation.
Bückmann, Tiemo; Kadic, Muamer; Schittny, Robert; Wegener, Martin
2015-04-21
Spatial coordinate transformations have helped simplifying mathematical issues and solving complex boundary-value problems in physics for decades already. More recently, material-parameter transformations have also become an intuitive and powerful engineering tool for designing inhomogeneous and anisotropic material distributions that perform wanted functions, e.g., invisibility cloaking. A necessary mathematical prerequisite for this approach to work is that the underlying equations are form invariant with respect to general coordinate transformations. Unfortunately, this condition is not fulfilled in elastic-solid mechanics for materials that can be described by ordinary elasticity tensors. Here, we introduce a different and simpler approach. We directly transform the lattice points of a 2D discrete lattice composed of a single constituent material, while keeping the properties of the elements connecting the lattice points the same. After showing that the approach works in various areas, we focus on elastic-solid mechanics. As a demanding example, we cloak a void in an effective elastic material with respect to static uniaxial compression. Corresponding numerical calculations and experiments on polymer structures made by 3D printing are presented. The cloaking quality is quantified by comparing the average relative SD of the strain vectors outside of the cloaked void with respect to the homogeneous reference lattice. Theory and experiment agree and exhibit very good cloaking performance. PMID:25848021
Mechanical cloak design by direct lattice transformation
Bückmann, Tiemo; Kadic, Muamer; Schittny, Robert; Wegener, Martin
2015-01-01
Spatial coordinate transformations have helped simplifying mathematical issues and solving complex boundary-value problems in physics for decades already. More recently, material-parameter transformations have also become an intuitive and powerful engineering tool for designing inhomogeneous and anisotropic material distributions that perform wanted functions, e.g., invisibility cloaking. A necessary mathematical prerequisite for this approach to work is that the underlying equations are form invariant with respect to general coordinate transformations. Unfortunately, this condition is not fulfilled in elastic–solid mechanics for materials that can be described by ordinary elasticity tensors. Here, we introduce a different and simpler approach. We directly transform the lattice points of a 2D discrete lattice composed of a single constituent material, while keeping the properties of the elements connecting the lattice points the same. After showing that the approach works in various areas, we focus on elastic–solid mechanics. As a demanding example, we cloak a void in an effective elastic material with respect to static uniaxial compression. Corresponding numerical calculations and experiments on polymer structures made by 3D printing are presented. The cloaking quality is quantified by comparing the average relative SD of the strain vectors outside of the cloaked void with respect to the homogeneous reference lattice. Theory and experiment agree and exhibit very good cloaking performance. PMID:25848021
Multiple Lattice Model for Influenza Spreading
Liccardo, Antonella; Fierro, Annalisa
2015-01-01
Behavioral differences among age classes, together with the natural tendency of individuals to prefer contacts with individuals of similar age, naturally point to the existence of a community structure in the population network, in which each community can be identified with a different age class. Data on age-dependent contact patterns also reveal how relevant is the role of the population age structure in shaping the spreading of an infectious disease. In the present paper we propose a simple model for epidemic spreading, in which a contact network with an intrinsic community structure is coupled with a simple stochastic SIR model for the epidemic spreading. The population is divided in 4 different age-communities and hosted on a multiple lattice, each community occupying a specific age-lattice. Individuals are allowed to move freely to nearest neighbor empty sites on the age-lattice. Different communities are connected with each other by means of inter-lattices edges, with a different number of external links connecting different age class populations. The parameters of the contact network model are fixed by requiring the simulated data to fully reproduce the contact patterns matrices of the Polymod survey. The paper shows that adopting a topology which better implements the age-class community structure of the population, one gets a better agreement between experimental contact patterns and simulated data, and this also improves the accordance between simulated and experimental data on the epidemic spreading. PMID:26513580
Variational method for lattice spectroscopy with ghosts
Burch, Tommy; Hagen, Christian; Gattringer, Christof; Glozman, Leonid Ya.; Lang, C.B.
2006-01-01
We discuss the variational method used in lattice spectroscopy calculations. In particular we address the role of ghost contributions which appear in quenched or partially quenched simulations and have a nonstandard euclidean time dependence. We show that the ghosts can be separated from the physical states. Our result is illustrated with numerical data for the scalar meson.
A Lattice Boltzmann Method for Turbomachinery Simulations
NASA Technical Reports Server (NTRS)
Hsu, A. T.; Lopez, I.
2003-01-01
Lattice Boltzmann (LB) Method is a relatively new method for flow simulations. The start point of LB method is statistic mechanics and Boltzmann equation. The LB method tries to set up its model at molecular scale and simulate the flow at macroscopic scale. LBM has been applied to mostly incompressible flows and simple geometry.
A continuum model for interconnected lattice trusses
NASA Technical Reports Server (NTRS)
Balakrishnan, A. V.
1992-01-01
A continuum model for interconnected lattice trusses based on the 1D Timoshenko beam approximation is developed using the NASA-LRC Phase Zero Evolutionary Model. The continuum model dynamics is presented in the canonical wave-equation form in a Hilbert space.
A lattice gas model for thermohydrodynamics
Chen, Shiyi; Chen, Hudong; Doolen, G.D.; Gutman, S.; Lee, M.
1990-05-03
The FHP lattice gas model is extended to include a temperature variable in order to study thermohydrodynamics. The compressible Navier-Stokes equations are derived using a Chapman-Enskog expansion. Heat conduction and convention problems are investigated, including Benard convention. It is shown that the usual FHP rescaling procedure can be avoided by controlling the temperature. 20 refs., 12 figs.
LATTICE QCD THERMODYNAMICS WITH WILSON QUARKS.
EJIRI,S.
2007-11-20
We review studies of QCD thermodynamics by lattice QCD simulations with dynamical Wilson quarks. After explaining the basic properties of QCD with Wilson quarks at finite temperature including the phase structure and the scaling properties around the chiral phase transition, we discuss the critical temperature, the equation of state and heavy-quark free energies.
Random template banks and relaxed lattice coverings
Messenger, C.; Prix, R.; Papa, M. A.
2009-05-15
Template-based searches for gravitational waves are often limited by the computational cost associated with searching large parameter spaces. The study of efficient template banks, in the sense of using the smallest number of templates, is therefore of great practical interest. The traditional approach to template-bank construction requires every point in parameter space to be covered by at least one template, which rapidly becomes inefficient at higher dimensions. Here we study an alternative approach, where any point in parameter space is covered only with a given probability {eta}<1. We find that by giving up complete coverage in this way, large reductions in the number of templates are possible, especially at higher dimensions. The prime examples studied here are random template banks in which templates are placed randomly with uniform probability over the parameter space. In addition to its obvious simplicity, this method turns out to be surprisingly efficient. We analyze the statistical properties of such random template banks, and compare their efficiency to traditional lattice coverings. We further study relaxed lattice coverings (using Z{sub n} and A{sub n}* lattices), which similarly cover any signal location only with probability {eta}. The relaxed A{sub n}* lattice is found to yield the most efficient template banks at low dimensions (n < or approx. 10), while random template banks increasingly outperform any other method at higher dimensions.
Method of descent for integrable lattices
NASA Astrophysics Data System (ADS)
Bogoyavlensky, Oleg
2009-05-01
A method of descent for constructing integrable Hamiltonian systems is introduced. The derived periodic and nonperiodic lattices possess Lax representations with spectral parameter and have plenty of first integrals. Examples of Liouville-integrable four-dimensional Hamiltonian Lotka-Volterra systems are presented.
Entropic pressure in lattice models for polymers
NASA Astrophysics Data System (ADS)
Hammer, Yosi; Kantor, Yacov
2014-11-01
In lattice models, local pressure on a surface is derived from the change in the free energy of the system due to the exclusion of a certain boundary site, while the total force on the surface can be obtained by a similar exclusion of all surface sites. In these definitions, while the total force on the surface of a lattice system matches the force measured in a continuous system, the local pressure does not. Moreover, in a lattice system, the sum of the local pressures is not equal to the total force as is required in a continuous system. The difference is caused by correlation between occupations of surface sites as well as finite displacement of surface elements used in the definition of the pressures and the force. This problem is particularly acute in the studies of entropic pressure of polymers represented by random or self-avoiding walks on a lattice. We propose a modified expression for the local pressure which satisfies the proper relation between the pressure and the total force, and show that for a single ideal polymer in the presence of scale-invariant boundaries it produces quantitatively correct values for continuous systems. The required correction to the pressure is non-local, i.e., it depends on long range correlations between contact points of the polymer and the surface.
Entropic pressure in lattice models for polymers.
Hammer, Yosi; Kantor, Yacov
2014-11-28
In lattice models, local pressure on a surface is derived from the change in the free energy of the system due to the exclusion of a certain boundary site, while the total force on the surface can be obtained by a similar exclusion of all surface sites. In these definitions, while the total force on the surface of a lattice system matches the force measured in a continuous system, the local pressure does not. Moreover, in a lattice system, the sum of the local pressures is not equal to the total force as is required in a continuous system. The difference is caused by correlation between occupations of surface sites as well as finite displacement of surface elements used in the definition of the pressures and the force. This problem is particularly acute in the studies of entropic pressure of polymers represented by random or self-avoiding walks on a lattice. We propose a modified expression for the local pressure which satisfies the proper relation between the pressure and the total force, and show that for a single ideal polymer in the presence of scale-invariant boundaries it produces quantitatively correct values for continuous systems. The required correction to the pressure is non-local, i.e., it depends on long range correlations between contact points of the polymer and the surface. PMID:25429960
Visualization Tools for Lattice QCD - Final Report
Massimo Di Pierro
2012-03-15
Our research project is about the development of visualization tools for Lattice QCD. We developed various tools by extending existing libraries, adding new algorithms, exposing new APIs, and creating web interfaces (including the new NERSC gauge connection web site). Our tools cover the full stack of operations from automating download of data, to generating VTK files (topological charge, plaquette, Polyakov lines, quark and meson propagators, currents), to turning the VTK files into images, movies, and web pages. Some of the tools have their own web interfaces. Some Lattice QCD visualization have been created in the past but, to our knowledge, our tools are the only ones of their kind since they are general purpose, customizable, and relatively easy to use. We believe they will be valuable to physicists working in the field. They can be used to better teach Lattice QCD concepts to new graduate students; they can be used to observe the changes in topological charge density and detect possible sources of bias in computations; they can be used to observe the convergence of the algorithms at a local level and determine possible problems; they can be used to probe heavy-light mesons with currents and determine their spatial distribution; they can be used to detect corrupted gauge configurations. There are some indirect results of this grant that will benefit a broader audience than Lattice QCD physicists.
Phonons and elasticity in critically coordinated lattices
NASA Astrophysics Data System (ADS)
Lubensky, T. C.; Kane, C. L.; Mao, Xiaoming; Souslov, A.; Sun, Kai
2015-07-01
Much of our understanding of vibrational excitations and elasticity is based upon analysis of frames consisting of sites connected by bonds occupied by central-force springs, the stability of which depends on the average number of neighbors per site z. When z < zc ≈ 2d, where d is the spatial dimension, frames are unstable with respect to internal deformations. This pedagogical review focuses on the properties of frames with z at or near zc, which model systems like randomly packed spheres near jamming and network glasses. Using an index theorem, N0 -NS = dN -NB relating the number of sites, N, and number of bonds, NB, to the number, N0, of modes of zero energy and the number, NS, of states of self stress, in which springs can be under positive or negative tension while forces on sites remain zero, it explores the properties of periodic square, kagome, and related lattices for which z = zc and the relation between states of self stress and zero modes in periodic lattices to the surface zero modes of finite free lattices (with free boundary conditions). It shows how modifications to the periodic kagome lattice can eliminate all but trivial translational zero modes and create topologically distinct classes, analogous to those of topological insulators, with protected zero modes at free boundaries and at interfaces between different topological classes.
Heavy quark masses from lattice QCD
NASA Astrophysics Data System (ADS)
Lytle, Andrew T.
2016-07-01
Progress in quark mass determinations from lattice QCD is reviewed, focusing on results for charm and bottom mass. These are of particular interest for precision Higgs studies. Recent determinations have achieved percent-level uncertainties with controlled systematics. Future prospects for these calculations are also discussed.
Progress in kaon physics on the lattice
NASA Astrophysics Data System (ADS)
Lee, Weonjong
2006-12-01
We review recent progress in calculating kaon spectrum, pseudoscalar meson decay constants, B K , ɛ ɛ, K ππ matrix elements, kaon semileptonic form factors, and moments of kaon distribution amplitudes on the lattice. We also address the issue of how best to improve the staggered fermion formulation for the action and operators.
Lattice Multiplication in a Preservice Classroom
ERIC Educational Resources Information Center
Nugent, Patricia M.
2007-01-01
This article discusses the algorithm for multiplication that is referred to as lattice multiplication. Evidence of how the author's preservice students' conceptual understanding of the algorithm grew through the semester is given. In addition, the author extends the conceptualization of the algorithm from the multiplication of whole numbers to the…
Scalar meson spectroscopy with lattice staggered fermions
Bernard, Claude; DeTar, Carleton; Fu Ziwen; Prelovsek, Sasa
2007-11-01
With sufficiently light up and down quarks the isovector (a{sub 0}) and isosinglet (f{sub 0}) scalar meson propagators are dominated at large distance by two-meson states. In the staggered-fermion formulation of lattice quantum chromodynamics, taste-symmetry breaking causes a proliferation of two-meson states that further complicates the analysis of these channels. Many of them are unphysical artifacts of the lattice approximation. They are expected to disappear in the continuum limit. The staggered-fermion fourth-root procedure has its purported counterpart in rooted staggered chiral perturbation theory (rS{chi}PT). Fortunately, the rooted theory provides a strict framework that permits the analysis of scalar meson correlators in terms of only a small number of low-energy couplings. Thus the analysis of the point-to-point scalar meson correlators in this context gives a useful consistency check of the fourth-root procedure and its proposed chiral realization. Through numerical simulation we have measured correlators for both the a{sub 0} and f{sub 0} channels in the 'Asqtad' improved staggered-fermion formulation in a lattice ensemble with lattice spacing a=0.12 fm. We analyze those correlators in the context of rS{chi}PT and obtain values of the low-energy chiral couplings that are reasonably consistent with previous determinations.
Arab-Chapelet, B; Martin, P M; Costenoble, S; Delahaye, T; Scheinost, A C; Grandjean, S; Abraham, F
2016-04-28
Mixed actinide(III,IV) oxalates of the general formula M2.2UAn(C2O4)5·nH2O (An = Pu or Am and M = H3O(+) and N2H5(+)) have been quantitatively precipitated by oxalic precipitation in nitric acid medium (yield >99%). Thorough multiscale structural characterization using XRD and XAS measurements confirmed the existence of mixed actinide oxalate solid solutions. The XANES analysis confirmed that the oxidation states of the metallic cations, tetravalent for uranium and trivalent for plutonium and americium, are maintained during the precipitation step. EXAFS measurements show that the local environments around U(+IV), Pu(+III) and Am(+III) are comparable, and the actinides are surrounded by ten oxygen atoms from five bidentate oxalate anions. The mean metal-oxygen distances obtained by XAS measurements are in agreement with those calculated from XRD lattice parameters. PMID:26979820
A low-emittance lattice for SPEAR
NASA Astrophysics Data System (ADS)
Safranek, J.; Wiedemann, H.
1992-08-01
The design and implementation of a low emittance lattice for the SPEAR storage ring including measurements of the performance of the lattice are presented [J. Safranek, Ph.D. thesis, Stanford University, 1991]. The low emittance lattice is designed to optimize the performance of SPEAR as a synchrotron radiation source while keeping SPEAR hardware changes at a minimum. The horizontal emittance of the electron beam in the low emittance lattice is reduced by a factor of 4 from the previous lattice. This reduces the typical horizontal source size and divergence of the photon beams by a factor of 2 each and increases the photon beam brightness. At 3 GeV the horizontal emittance is 129π nm rad, which makes the low emittance lattice the lowest emittance, running synchrotron radiation source in the world in the 1.5 to 4.0 GeV energy range for the emittance scaled to 3 GeV. The measured vertical emittance was reduced to half that typically seen at SPEAR in the past. The brightness of the photon beams was further increased by reducing βy at the insertion devices to 1.1 m and reducing the energy dispersion at the insertion devices by more than a factor of 2 on average. The horizontal dispersion at the rf cavities was reduced by a factor of nearly 4 which gives much less problems with synchrobetatron resonances. The dynamic and physical apertures of the lattice are large, giving long beam lifetimes and easy injection of electrons. The measurements of the linear optics and intensity dependent phenomena gave reasonable agreement with the design. The overall performance of the machine was very good. Injection rates of 10 to 20 mA/min and larger were achieved routinely, and 100 mA total current was stored. Repeated ramping of stored beam from the injection energy of 2.3 GeV to the running energy of 3.0 GeV was achieved with very little beam loss. This low emittance configuration is expected to be the operating configuration for SPEAR starting in January 1992.
NASA Astrophysics Data System (ADS)
Orszag, M.; Retamal, J. C.; Saavedra, C.; Wallentowitz, S.
2007-06-01
All the 50 years of conscious pondering did not bring me nearer to an answer to the question `what is light quanta?'. Nowadays, every rascal believes, he knows it, however, he is mistaken. (A Einstein, 1951 in a letter to M Besso) Quantum optics has played a key role in physics in the last several decades. On the other hand, in these early decades of the information age, the flow of information is becoming more and more central to our daily life. Thus, the related fields of quantum information theory as well as Bose-Einstein condensation have acquired tremendous importance in the last couple of decades. In Quantum Optics III, a fusion of these fields appears in a natural way. Quantum Optics III was held in Pucón, Chile, in 27-30 of November, 2006. This beautiful location in the south of Chile is near the lake Villarrica and below the snow covered volcano of the same name. This fantastic environment contributed to a relaxed atmosphere, suitable for informal discussion and for the students to have a chance to meet the key figures in the field. The previous Quantum Optics conferences took place in Santiago, Chile (Quantum Optics I, 2000) and Cozumel, Mexico (Quantum Optics II, 2004). About 115 participants from 19 countries attended and participated in the meeting to discuss a wide variety of topics such as quantum-information processing, experiments related to non-linear optics and squeezing, various aspects of entanglement including its sudden death, correlated twin-photon experiments, light storage, decoherence-free subspaces, Bose-Einstein condensation, discrete Wigner functions and many more. There was a strong Latin-American participation from Argentina, Brazil, Chile, Colombia, Peru, Uruguay, Venezuela and Mexico, as well as from Europe, USA, China, and Australia. New experimental and theoretical results were presented at the conference. In Latin-America a quiet revolution has taken place in the last twenty years. Several groups working in quantum optics and
Force Evaluation in the Lattice Boltzmann Method Involving Curved Geometry
NASA Technical Reports Server (NTRS)
Mei, Renwei; Yu, Dazhi; Shyy, Wei; Luo, Li-Shi; Bushnell, Dennis M. (Technical Monitor)
2002-01-01
The present work investigates two approaches for force evaluation in the lattice Boltzmann equation: the momentum- exchange method and the stress-integration method on the surface of a body. The boundary condition for the particle distribution functions on curved geometries is handled with second order accuracy based on our recent works. The stress-integration method is computationally laborious for two-dimensional flows and in general difficult to implement for three-dimensional flows, while the momentum-exchange method is reliable, accurate, and easy to implement for both two-dimensional and three-dimensional flows. Several test cases are selected to evaluate the present methods, including: (i) two-dimensional pressure-driven channel flow; (ii) two-dimensional uniform flow past a column of cylinders; (iii) two-dimensional flow past a cylinder asymmetrically placed in a channel (with vortex shedding); (iv) three-dimensional pressure-driven flow in a circular pipe; and (v) three-dimensional flow past a sphere. The drag evaluated by using the momentum-exchange method agrees well with the exact or other published results.
Force evaluation in the lattice Boltzmann method involving curved geometry
NASA Astrophysics Data System (ADS)
Mei, Renwei; Yu, Dazhi; Shyy, Wei; Luo, Li-Shi
2002-04-01
The present work investigates two approaches for force evaluation in the lattice Boltzmann equation: the momentum-exchange method and the stress-integration method on the surface of a body. The boundary condition for the particle distribution functions on curved geometries is handled with second-order accuracy based on our recent works [Mei et al., J. Comput. Phys. 155, 307 (1999); ibid. 161, 680 (2000)]. The stress-integration method is computationally laborious for two-dimensional flows and in general difficult to implement for three-dimensional flows, while the momentum-exchange method is reliable, accurate, and easy to implement for both two-dimensional and three-dimensional flows. Several test cases are selected to evaluate the present methods, including: (i) two-dimensional pressure-driven channel flow; (ii) two-dimensional uniform flow past a column of cylinders; (iii) two-dimensional flow past a cylinder asymmetrically placed in a channel (with vortex shedding); (iv) three-dimensional pressure-driven flow in a circular pipe; and (v) three-dimensional flow past a sphere. The drag evaluated by using the momentum-exchange method agrees well with the exact or other published results.
Phase space lattices and integrable nonlinear wave equations
NASA Astrophysics Data System (ADS)
Tracy, Eugene; Zobin, Nahum
2003-10-01
Nonlinear wave equations in fluids and plasmas that are integrable by Inverse Scattering Theory (IST), such as the Korteweg-deVries and nonlinear Schrodinger equations, are known to be infinite-dimensional Hamiltonian systems [1]. These are of interest physically because they predict new phenomena not present in linear wave theories, such as solitons and rogue waves. The IST method provides solutions of these equations in terms of a special class of functions called Riemann theta functions. The usual approach to the theory of theta functions tends to obscure the underlying phase space structure. A theory due to Mumford and Igusa [2], however shows that the theta functions arise naturally in the study of phase space lattices. We will describe this theory, as well as potential applications to nonlinear signal processing and the statistical theory of nonlinear waves. 1] , S. Novikov, S. V. Manakov, L. P. Pitaevskii and V. E. Zakharov, Theory of solitons: the inverse scattering method (Consultants Bureau, New York, 1984). 2] D. Mumford, Tata lectures on theta, Vols. I-III (Birkhauser); J. Igusa, Theta functions (Springer-Verlag, New York, 1972).
Multiple anisotropic collisions for advection-diffusion Lattice Boltzmann schemes
NASA Astrophysics Data System (ADS)
Ginzburg, Irina
2013-01-01
This paper develops a symmetrized framework for the analysis of the anisotropic advection-diffusion Lattice Boltzmann schemes. Two main approaches build the anisotropic diffusion coefficients either from the anisotropic anti-symmetric collision matrix or from the anisotropic symmetric equilibrium distribution. We combine and extend existing approaches for all commonly used velocity sets, prescribe most general equilibrium and build the diffusion and numerical-diffusion forms, then derive and compare solvability conditions, examine available anisotropy and stable velocity magnitudes in the presence of advection. Besides the deterioration of accuracy, the numerical diffusion dictates the stable velocity range. Three techniques are proposed for its elimination: (i) velocity-dependent relaxation entries; (ii) their combination with the coordinate-link equilibrium correction; and (iii) equilibrium correction for all links. Two first techniques are also available for the minimal (coordinate) velocity sets. Even then, the two-relaxation-times model with the isotropic rates often gains in effective stability and accuracy. The key point is that the symmetric collision mode does not modify the modeled diffusion tensor but it controls the effective accuracy and stability, via eigenvalue combinations of the opposite parity eigenmodes. We propose to reduce the eigenvalue spectrum by properly combining different anisotropic collision elements. The stability role of the symmetric, multiple-relaxation-times component, is further investigated with the exact von Neumann stability analysis developed in diffusion-dominant limit.
Invariant patterns in crystal lattices: Implications for protein folding algorithms
HART,WILLIAM E.; ISTRAIL,SORIN
2000-06-01
Crystal lattices are infinite periodic graphs that occur naturally in a variety of geometries and which are of fundamental importance in polymer science. Discrete models of protein folding use crystal lattices to define the space of protein conformations. Because various crystal lattices provide discretizations of the same physical phenomenon, it is reasonable to expect that there will exist invariants across lattices related to fundamental properties of the protein folding process. This paper considers whether performance-guaranteed approximability is such an invariant for HP lattice models. The authors define a master approximation algorithm that has provable performance guarantees provided that a specific sublattice exists within a given lattice. They describe a broad class of crystal lattices that are approximable, which further suggests that approximability is a general property of HP lattice models.
Transverse momentum distributions inside the nucleon from lattice QCD
Musch, B. U.; Haegler, Ph.; Negele, J. W.; Schaefer, A.
2011-07-15
We study transverse momentum dependent parton distribution functions (TMDs) with non-local operators in lattice QCD, using MILC/LHPC lattices. Results obtained with a simplified operator geometry show visible dipole deformations of spin-dependent quark momentum densities.
5. VIEW FROM THE SOUTHEAST, SHOWING REPLACEMENT OF LATTICE PANELS ...
5. VIEW FROM THE SOUTHEAST, SHOWING REPLACEMENT OF LATTICE PANELS WITH CONCRETE PIERS AND ARCHED LATTICE PANELS, PRIOR TO 1908 ALTERATIONS - Ralph M. Munroe House, 3485 Main Highway, Coconut Grove, Miami, Miami-Dade County, FL
Detail of west end of movable span. Shows lattice beams. ...
Detail of west end of movable span. Shows lattice beams. Latticed portal. Adjustable tension members connecting top chords, and metal floor beams looking south from navy land. - Naval Supply Annex Stockton, Rough & Ready Island, Stockton, San Joaquin County, CA
A transfer-matrix study of directed lattice animals and directed percolation on a square lattice
NASA Astrophysics Data System (ADS)
Knežević, Dragica; Knežević, Milan
2016-03-01
We studied the large-scale properties of directed lattice animals and directed percolation on a square lattice. Using a transfer-matrix approach on strips of finite widths, we generated relatively long sequences of estimates for effective values of critical fugacity, percolation threshold and correlation length critical exponents. We applied two different extrapolation methods to obtain estimates for infinite systems. The precision of our final estimates is comparable to (or better than) the precision of the best currently available results.
Ultracold quantum gases and lattice systems: quantum simulation of lattice gauge theories
NASA Astrophysics Data System (ADS)
Wiese, U.-J.
2013-11-01
Abelian and non-Abelian gauge theories are of central importance in many areas of physics. In condensed matter physics, Abelian U(1) lattice gauge theories arise in the description of certain quantum spin liquids. In quantum information theory, Kitaev's toric code is a Z(2) lattice gauge theory. In particle physics, Quantum Chromodynamics (QCD), the non-Abelian SU(3) gauge theory of the strong interactions between quarks and gluons, is non-perturbatively regularized on a lattice. Quantum link models extend the concept of lattice gauge theories beyond the Wilson formulation, and are well suited for both digital and analog quantum simulation using ultracold atomic gases in optical lattices. Since quantum simulators do not suffer from the notorious sign problem, they open the door to studies of the real-time evolution of strongly coupled quantum systems, which are impossible with classical simulation methods. A plethora of interesting lattice gauge theories suggests itself for quantum simulation, which should allow us to address very challenging problems, ranging from confinement and deconfinement, or chiral symmetry breaking and its restoration at finite baryon density, to color superconductivity and the real-time evolution of heavy-ion collisions, first in simpler model gauge theories and ultimately in QCD.
Regularization methods for Nuclear Lattice Effective Field Theory
NASA Astrophysics Data System (ADS)
Klein, Nico; Lee, Dean; Liu, Weitao; Meißner, Ulf-G.
2015-07-01
We investigate Nuclear Lattice Effective Field Theory for the two-body system for several lattice spacings at lowest order in the pionless as well as in the pionful theory. We discuss issues of regularizations and predictions for the effective range expansion. In the pionless case, a simple Gaussian smearing allows to demonstrate lattice spacing independence over a wide range of lattice spacings. We show that regularization methods known from the continuum formulation are necessary as well as feasible for the pionful approach.
Connection Between the Lattice Boltzmann Equation and the Beam Scheme
NASA Technical Reports Server (NTRS)
Xu, Kun; Luo, Li-Shi
1999-01-01
In this paper we analyze and compare the lattice Boltzmann equation with the beam scheme in details. We notice the similarity and differences between the lattice Boltzmann equation and the beam scheme. We show that the accuracy of the lattice Boltzmann equation is indeed second order in space. We discuss the advantages and limitations of lattice Boltzmann equation and the beam scheme. Based on our analysis, we propose an improved multi-dimensional beam scheme.
Hadronic Vacuum Polarization Contribution to g-2 from the Lattice
Dru Renner, Xu Feng, Marcus Petschlies, Karl Jansen
2012-05-01
We give a short description of the present situation of lattice QCD simulations. We then focus on the computation of the anomalous magnetic moment of the muon using lattice techniques. We demonstrate that by employing improved observables for the muon anomalous magnetic moment, a significant reduction of the lattice error can be obtained. This provides a promising scenario that the accuracy of lattice calculations can match the experimental errors.
Experimental evidence for lattice effects in high temperature superconductors
Billinge, S.J.L.; Kwei, G.H.; Thompson, J.D.
1994-01-18
We present an overview of the experimental evidence for a role of the lattice in the mechanism of high temperature superconductivity. It appears unlikely that a solely conventional electron-phonon interaction produces the pairing. However, there is ample evidence of strong electron and spin to lattice coupling and observations of a response of the lattice to the electronic state. We draw attention to the importance of the local structure in discussions of lattice effects in high-{Tc} superconductivity.
Cranial mononeuropathy III - diabetic type
Diabetic third nerve palsy; Pupil-sparing third cranial nerve palsy ... Cranial mononeuropathy III - diabetic type -- is a mononeuropathy . This means that only one nerve is damaged. The condition affects the third cranial (oculomotor) ...
Spanning trees on graphs and lattices in d dimensions
NASA Astrophysics Data System (ADS)
Shrock, Robert; Wu, F. Y.
2000-06-01
The problem of enumerating spanning trees on graphs and lattices is considered. We obtain bounds on the number of spanning trees NST and establish inequalities relating the numbers of spanning trees of different graphs or lattices. A general formulation is presented for the enumeration of spanning trees on lattices in d≥2 dimensions, and is applied to the hypercubic, body-centred cubic, face-centred cubic and specific planar lattices including the kagomé, diced, 4-8-8 (bathroom-tile), Union Jack and 3-12-12 lattices. This leads to closed-form expressions for NST for these lattices of finite sizes. We prove a theorem concerning the classes of graphs and lattices →∞, where zL is a finite non-zero constant. This includes the bulk limit of lattices in any spatial dimension, and also sections of lattices whose lengths in some dimensions go to infinity while others are finite. We evaluate zL exactly for the lattices we consider, and discuss the dependence of zL on d and the lattice coordination number. We also establish a relation connecting zL to the free energy of the critical Ising model for planar lattices.
Chaotic dynamics in a two-dimensional optical lattice.
Horsley, Eric; Koppell, Stewart; Reichl, L E
2014-01-01
The classical nonlinear dynamics of a dilute gas of rubidium atoms in an optical lattice is studied for a range of polarizations of the laser beams forming the lattice. The dynamics ranges from integrable to chaotic, and mechanisms leading to the onset of chaos in the lattice are described. PMID:24580307
Coincidence lattice model for the structure and energy of grain boundaries
Brokman, A.; Balluffi, R.W.
1981-01-01
It is proposed that, to a good approximation, the construction of a boundary can be described in terms of three basic steps: (1) a rigid body joining of two perfect crystals along the boundary plane (Step I); (2) a primary relaxation (Step II) consisting of relaxations in the boundary centered on O-Lattice elements which act to improve lattice matching in these regions; and (3) a possible secondary relaxation (Step III) which produces the final structure composed of patches of a low ..sigma.. boundary and secondary grain boundary dislocations. The energy after Step I is obtained by summing pairwise interactions across the boundary and is found to be relatively low for a number of low ..sigma.. boundaries and to approach a larger constant value for all large ..sigma.. boundaries. The energy decrease due to Step II varies monotonically with crystal misorientation according to a Read-Shockley function, and the energy decrease associated with Step III produces cusps in the energy versus misorientation curve at misorientations corresponding to low ..sigma.. boundaries. The model appears to be consistent with the present knowledge of boundary structure and energy, and its general applicability is discussed.
Layered transition metal dichalcogenides: promising near-lattice-matched substrates for GaN growth
Gupta, Priti; Rahman, A. A.; Subramanian, Shruti; Gupta, Shalini; Thamizhavel, Arumugam; Orlova, Tatyana; Rouvimov, Sergei; Vishwanath, Suresh; Protasenko, Vladimir; Laskar, Masihhur R.; Xing, Huili Grace; Jena, Debdeep; Bhattacharya, Arnab
2016-01-01
Most III-nitride semiconductors are grown on non-lattice-matched substrates like sapphire or silicon due to the extreme difficulty of obtaining a native GaN substrate. We show that several layered transition-metal dichalcogenides are closely lattice-matched to GaN and report the growth of GaN on a range of such layered materials. We report detailed studies of the growth of GaN on mechanically-exfoliated flakes WS2 and MoS2 by metalorganic vapour phase epitaxy. Structural and optical characterization show that strain-free, single-crystal islands of GaN are obtained on the underlying chalcogenide flakes. We obtain strong near-band-edge emission from these layers, and analyse their temperature-dependent photoluminescence properties. We also report a proof-of-concept demonstration of large-area growth of GaN on CVD MoS2. Our results show that the transition-metal dichalcogenides can serve as novel near-lattice-matched substrates for nitride growth. PMID:27025461
Layered transition metal dichalcogenides: promising near-lattice-matched substrates for GaN growth
NASA Astrophysics Data System (ADS)
Gupta, Priti; Rahman, A. A.; Subramanian, Shruti; Gupta, Shalini; Thamizhavel, Arumugam; Orlova, Tatyana; Rouvimov, Sergei; Vishwanath, Suresh; Protasenko, Vladimir; Laskar, Masihhur R.; Xing, Huili Grace; Jena, Debdeep; Bhattacharya, Arnab
2016-03-01
Most III-nitride semiconductors are grown on non-lattice-matched substrates like sapphire or silicon due to the extreme difficulty of obtaining a native GaN substrate. We show that several layered transition-metal dichalcogenides are closely lattice-matched to GaN and report the growth of GaN on a range of such layered materials. We report detailed studies of the growth of GaN on mechanically-exfoliated flakes WS2 and MoS2 by metalorganic vapour phase epitaxy. Structural and optical characterization show that strain-free, single-crystal islands of GaN are obtained on the underlying chalcogenide flakes. We obtain strong near-band-edge emission from these layers, and analyse their temperature-dependent photoluminescence properties. We also report a proof-of-concept demonstration of large-area growth of GaN on CVD MoS2. Our results show that the transition-metal dichalcogenides can serve as novel near-lattice-matched substrates for nitride growth.
Geometric entanglement and quantum phase transitions in two-dimensional quantum lattice models
NASA Astrophysics Data System (ADS)
Shi, Qian-Qian; Wang, Hong-Lei; Li, Sheng-Hao; Cho, Sam Young; Batchelor, Murray T.; Zhou, Huan-Qiang
2016-06-01
Geometric entanglement (GE), as a measure of multipartite entanglement, has been investigated as a universal tool to detect phase transitions in quantum many-body lattice models. In this paper we outline a systematic method to compute GE for two-dimensional (2D) quantum many-body lattice models based on the translational invariant structure of infinite projected entangled pair state (iPEPS) representations. By employing this method, the q -state quantum Potts model on the square lattice with q ∈{2 ,3 ,4 ,5 } is investigated as a prototypical example. Further, we have explored three 2D Heisenberg models: the antiferromagnetic spin-1/2 X X X and anisotropic X Y X models in an external magnetic field, and the antiferromagnetic spin-1 X X Z model. We find that continuous GE does not guarantee a continuous phase transition across a phase transition point. We observe and thus classify three different types of continuous GE across a phase transition point: (i) GE is continuous with maximum value at the transition point and the phase transition is continuous, (ii) GE is continuous with maximum value at the transition point but the phase transition is discontinuous, and (iii) GE is continuous with nonmaximum value at the transition point and the phase transition is continuous. For the models under consideration, we find that the second and the third types are related to a point of dual symmetry and a fully polarized phase, respectively.
Shi, Bingjie; Liu, Kai; Wu, Lingling; Li, Weiqiang; Smeaton, Christina M; Beard, Brian L; Johnson, Clark M; Roden, Eric E; Van Cappellen, Philippe
2016-08-16
We report on stable Fe isotope fractionation during microbial and chemical reduction of structural Fe(III) in nontronite NAu-1. (56)Fe/(54)Fe fractionation factors between aqueous Fe(II) and structural Fe(III) ranged from -1.2 to +0.8‰. Microbial (Shewanella oneidensis and Geobacter sulfurreducens) and chemical (dithionite) reduction experiments revealed a two-stage process. Stage 1 was characterized by rapid reduction of a finite Fe(III) pool along the edges of the clay particles, accompanied by a limited release to solution of Fe(II), which partially adsorbed onto basal planes. Stable Fe isotope compositions revealed that electron transfer and atom exchange (ETAE) occurred between edge-bound Fe(II) and octahedral (structural) Fe(III) within the clay lattice, as well as between aqueous Fe(II) and structural Fe(III) via a transient sorbed phase. The isotopic fractionation factors decreased with increasing extent of reduction as a result of the depletion of the finite bioavailable Fe(III) pool. During stage 2, microbial reduction was inhibited while chemical reduction continued. However, further ETAE between aqueous Fe(II) and structural Fe(III) was not observed. Our results imply that the pool of bioavailable Fe(III) is restricted to structural Fe sites located near the edges of the clay particles. Blockage of ETAE distinguishes Fe(III) reduction of layered clay minerals from that of Fe oxyhydroxides, where accumulation of structural Fe(II) is much more limited. PMID:27291525
Flux-line-lattice stability and dynamics
NASA Astrophysics Data System (ADS)
Glyde, H. R.; Moleko, L. K.; Findeisen, P.
1992-02-01
The mechanical stability of a flux-line lattice (FLL) having parameters appropriate for the high-Tc superconductors is determined using the self-consistent phonon theory of lattice dynamics. Nearly parallel flux lines (FL's) are assumed and FL pinning is neglected. The FLL becomes unstable when a phonon frequency goes to zero. At instability the rms vibrational amplitude diverges and the FL's can no longer be localized. In Bi2Sr2CaCuO2O8, the instability line as a function of temperature and magnetic field lies below but in reasonable agreement with the observed irreversibility line. In YBa2Cu3O7, it lies significantly below. The present instability line is a reliable upper bound to the FLL melting line. Identifying instability with melting, we find the Lindemann criterion of melting does not hold. However, the present instability lines and the melting lines obtained by Houghton et al. are found to have similar shape.
Thermal lattice Boltzmann method for complex microflows
NASA Astrophysics Data System (ADS)
Yasuoka, Haruka; Kaneda, Masayuki; Suga, Kazuhiko
2016-07-01
A methodology to simulate thermal fields in complex microflow geometries is proposed. For the flow fields, the regularized multiple-relaxation-time lattice Boltzmann method (LBM) is applied coupled with the diffusive-bounce-back boundary condition for wall boundaries. For the thermal fields, the regularized lattice Bhatnagar-Gross-Krook model is applied. For the thermal wall boundary condition, a newly developed boundary condition, which is a mixture of the diffuse scattering and constant temperature conditions, is applied. The proposed set of schemes is validated by reference data in the Fourier flows and square cylinder flows confined in a microchannel. The obtained results confirm that it is essential to apply the regularization to the thermal LBM for avoiding kinked temperature profiles in complex thermal flows. The proposed wall boundary condition is successful to obtain thermal jumps at the walls with good accuracy.